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class="pinned-header">Node.js v18.18.2</li> 115 116 <li class="picker-header"> 117 <a href="#"> 118 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 119 Table of contents 120 </a> 121 122 <div class="picker"><div class="toc"><ul> 123<li><span class="stability_2"><a href="#performance-measurement-apis">Performance measurement APIs</a></span> 124<ul> 125<li><a href="#perf_hooksperformance"><code>perf_hooks.performance</code></a> 126<ul> 127<li><a href="#performanceclearmarksname"><code>performance.clearMarks([name])</code></a></li> 128<li><a href="#performanceclearmeasuresname"><code>performance.clearMeasures([name])</code></a></li> 129<li><a href="#performanceclearresourcetimingsname"><code>performance.clearResourceTimings([name])</code></a></li> 130<li><a href="#performanceeventlooputilizationutilization1-utilization2"><code>performance.eventLoopUtilization([utilization1[, utilization2]])</code></a></li> 131<li><a href="#performancegetentries"><code>performance.getEntries()</code></a></li> 132<li><a href="#performancegetentriesbynamename-type"><code>performance.getEntriesByName(name[, type])</code></a></li> 133<li><a href="#performancegetentriesbytypetype"><code>performance.getEntriesByType(type)</code></a></li> 134<li><a href="#performancemarkname-options"><code>performance.mark([name[, options]])</code></a></li> 135<li><a href="#performancemarkresourcetimingtiminginfo-requestedurl-initiatortype-global-cachemode"><code>performance.markResourceTiming(timingInfo, requestedUrl, initiatorType, global, cacheMode)</code></a></li> 136<li><a href="#performancemeasurename-startmarkoroptions-endmark"><code>performance.measure(name[, startMarkOrOptions[, endMark]])</code></a></li> 137<li><a href="#performancenodetiming"><code>performance.nodeTiming</code></a></li> 138<li><a href="#performancenow"><code>performance.now()</code></a></li> 139<li><a href="#performancesetresourcetimingbuffersizemaxsize"><code>performance.setResourceTimingBufferSize(maxSize)</code></a></li> 140<li><a href="#performancetimeorigin"><code>performance.timeOrigin</code></a></li> 141<li><a href="#performancetimerifyfn-options"><code>performance.timerify(fn[, options])</code></a></li> 142<li><a href="#performancetojson"><code>performance.toJSON()</code></a> 143<ul> 144<li><a href="#event-resourcetimingbufferfull">Event: <code>'resourcetimingbufferfull'</code></a></li> 145</ul> 146</li> 147</ul> 148</li> 149<li><a href="#class-performanceentry">Class: <code>PerformanceEntry</code></a> 150<ul> 151<li><a href="#performanceentrydetail"><code>performanceEntry.detail</code></a></li> 152<li><a href="#performanceentryduration"><code>performanceEntry.duration</code></a></li> 153<li><a href="#performanceentryentrytype"><code>performanceEntry.entryType</code></a></li> 154<li><a href="#performanceentryflags"><code>performanceEntry.flags</code></a></li> 155<li><a href="#performanceentryname"><code>performanceEntry.name</code></a></li> 156<li><a href="#performanceentrykind"><code>performanceEntry.kind</code></a></li> 157<li><a href="#performanceentrystarttime"><code>performanceEntry.startTime</code></a></li> 158<li><a href="#garbage-collection-gc-details">Garbage Collection ('gc') Details</a></li> 159<li><a href="#http-http-details">HTTP ('http') Details</a></li> 160<li><a href="#http2-http2-details">HTTP/2 ('http2') Details</a></li> 161<li><a href="#timerify-function-details">Timerify ('function') Details</a></li> 162<li><a href="#net-net-details">Net ('net') Details</a></li> 163<li><a href="#dns-dns-details">DNS ('dns') Details</a></li> 164</ul> 165</li> 166<li><a href="#class-performancenodetiming">Class: <code>PerformanceNodeTiming</code></a> 167<ul> 168<li><a href="#performancenodetimingbootstrapcomplete"><code>performanceNodeTiming.bootstrapComplete</code></a></li> 169<li><a href="#performancenodetimingenvironment"><code>performanceNodeTiming.environment</code></a></li> 170<li><a href="#performancenodetimingidletime"><code>performanceNodeTiming.idleTime</code></a></li> 171<li><a href="#performancenodetimingloopexit"><code>performanceNodeTiming.loopExit</code></a></li> 172<li><a href="#performancenodetimingloopstart"><code>performanceNodeTiming.loopStart</code></a></li> 173<li><a href="#performancenodetimingnodestart"><code>performanceNodeTiming.nodeStart</code></a></li> 174<li><a href="#performancenodetimingv8start"><code>performanceNodeTiming.v8Start</code></a></li> 175</ul> 176</li> 177<li><a href="#class-performanceresourcetiming">Class: <code>PerformanceResourceTiming</code></a> 178<ul> 179<li><a href="#performanceresourcetimingworkerstart"><code>performanceResourceTiming.workerStart</code></a></li> 180<li><a href="#performanceresourcetimingredirectstart"><code>performanceResourceTiming.redirectStart</code></a></li> 181<li><a href="#performanceresourcetimingredirectend"><code>performanceResourceTiming.redirectEnd</code></a></li> 182<li><a href="#performanceresourcetimingfetchstart"><code>performanceResourceTiming.fetchStart</code></a></li> 183<li><a href="#performanceresourcetimingdomainlookupstart"><code>performanceResourceTiming.domainLookupStart</code></a></li> 184<li><a href="#performanceresourcetimingdomainlookupend"><code>performanceResourceTiming.domainLookupEnd</code></a></li> 185<li><a href="#performanceresourcetimingconnectstart"><code>performanceResourceTiming.connectStart</code></a></li> 186<li><a href="#performanceresourcetimingconnectend"><code>performanceResourceTiming.connectEnd</code></a></li> 187<li><a href="#performanceresourcetimingsecureconnectionstart"><code>performanceResourceTiming.secureConnectionStart</code></a></li> 188<li><a href="#performanceresourcetimingrequeststart"><code>performanceResourceTiming.requestStart</code></a></li> 189<li><a href="#performanceresourcetimingresponseend"><code>performanceResourceTiming.responseEnd</code></a></li> 190<li><a href="#performanceresourcetimingtransfersize"><code>performanceResourceTiming.transferSize</code></a></li> 191<li><a href="#performanceresourcetimingencodedbodysize"><code>performanceResourceTiming.encodedBodySize</code></a></li> 192<li><a href="#performanceresourcetimingdecodedbodysize"><code>performanceResourceTiming.decodedBodySize</code></a></li> 193<li><a href="#performanceresourcetimingtojson"><code>performanceResourceTiming.toJSON()</code></a></li> 194</ul> 195</li> 196<li><a href="#class-perf_hooksperformanceobserver">Class: <code>perf_hooks.PerformanceObserver</code></a> 197<ul> 198<li><a href="#performanceobserversupportedentrytypes"><code>PerformanceObserver.supportedEntryTypes</code></a></li> 199<li><a href="#new-performanceobservercallback"><code>new PerformanceObserver(callback)</code></a></li> 200<li><a href="#performanceobserverdisconnect"><code>performanceObserver.disconnect()</code></a></li> 201<li><a href="#performanceobserverobserveoptions"><code>performanceObserver.observe(options)</code></a></li> 202</ul> 203</li> 204<li><a href="#class-performanceobserverentrylist">Class: <code>PerformanceObserverEntryList</code></a> 205<ul> 206<li><a href="#performanceobserverentrylistgetentries"><code>performanceObserverEntryList.getEntries()</code></a></li> 207<li><a href="#performanceobserverentrylistgetentriesbynamename-type"><code>performanceObserverEntryList.getEntriesByName(name[, type])</code></a></li> 208<li><a href="#performanceobserverentrylistgetentriesbytypetype"><code>performanceObserverEntryList.getEntriesByType(type)</code></a></li> 209</ul> 210</li> 211<li><a href="#perf_hookscreatehistogramoptions"><code>perf_hooks.createHistogram([options])</code></a></li> 212<li><a href="#perf_hooksmonitoreventloopdelayoptions"><code>perf_hooks.monitorEventLoopDelay([options])</code></a></li> 213<li><a href="#class-histogram">Class: <code>Histogram</code></a> 214<ul> 215<li><a href="#histogramcount"><code>histogram.count</code></a></li> 216<li><a href="#histogramcountbigint"><code>histogram.countBigInt</code></a></li> 217<li><a href="#histogramexceeds"><code>histogram.exceeds</code></a></li> 218<li><a href="#histogramexceedsbigint"><code>histogram.exceedsBigInt</code></a></li> 219<li><a href="#histogrammax"><code>histogram.max</code></a></li> 220<li><a href="#histogrammaxbigint"><code>histogram.maxBigInt</code></a></li> 221<li><a href="#histogrammean"><code>histogram.mean</code></a></li> 222<li><a href="#histogrammin"><code>histogram.min</code></a></li> 223<li><a href="#histogramminbigint"><code>histogram.minBigInt</code></a></li> 224<li><a href="#histogrampercentilepercentile"><code>histogram.percentile(percentile)</code></a></li> 225<li><a href="#histogrampercentilebigintpercentile"><code>histogram.percentileBigInt(percentile)</code></a></li> 226<li><a href="#histogrampercentiles"><code>histogram.percentiles</code></a></li> 227<li><a href="#histogrampercentilesbigint"><code>histogram.percentilesBigInt</code></a></li> 228<li><a href="#histogramreset"><code>histogram.reset()</code></a></li> 229<li><a href="#histogramstddev"><code>histogram.stddev</code></a></li> 230</ul> 231</li> 232<li><a href="#class-intervalhistogram-extends-histogram">Class: <code>IntervalHistogram extends Histogram</code></a> 233<ul> 234<li><a href="#histogramdisable"><code>histogram.disable()</code></a></li> 235<li><a href="#histogramenable"><code>histogram.enable()</code></a></li> 236<li><a href="#cloning-an-intervalhistogram">Cloning an <code>IntervalHistogram</code></a></li> 237</ul> 238</li> 239<li><a href="#class-recordablehistogram-extends-histogram">Class: <code>RecordableHistogram extends Histogram</code></a> 240<ul> 241<li><a href="#histogramaddother"><code>histogram.add(other)</code></a></li> 242<li><a href="#histogramrecordval"><code>histogram.record(val)</code></a></li> 243<li><a href="#histogramrecorddelta"><code>histogram.recordDelta()</code></a></li> 244</ul> 245</li> 246<li><a href="#examples">Examples</a> 247<ul> 248<li><a href="#measuring-the-duration-of-async-operations">Measuring the duration of async operations</a></li> 249<li><a href="#measuring-how-long-it-takes-to-load-dependencies">Measuring how long it takes to load dependencies</a></li> 250<li><a href="#measuring-how-long-one-http-round-trip-takes">Measuring how long one HTTP round-trip takes</a></li> 251<li><a href="#measuring-how-long-the-netconnect-only-for-tcp-takes-when-the-connection-is-successful">Measuring how long the <code>net.connect</code> (only for TCP) takes when the connection is successful</a></li> 252<li><a href="#measuring-how-long-the-dns-takes-when-the-request-is-successful">Measuring how long the DNS takes when the request is successful</a></li> 253</ul> 254</li> 255</ul> 256</li> 257</ul></div></div> 258 </li> 259 260 261 <li class="picker-header"> 262 <a href="#"> 263 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 264 Index 265 </a> 266 267 <div class="picker"><ul> 268<li><a href="documentation.html" class="nav-documentation">About this documentation</a></li> 269<li><a href="synopsis.html" class="nav-synopsis">Usage and example</a></li> 270 271 <li> 272 <a href="index.html">Index</a> 273 </li> 274 </ul> 275 276<hr class="line"> 277<ul> 278<li><a href="assert.html" class="nav-assert">Assertion testing</a></li> 279<li><a href="async_context.html" class="nav-async_context">Asynchronous context tracking</a></li> 280<li><a href="async_hooks.html" class="nav-async_hooks">Async hooks</a></li> 281<li><a href="buffer.html" class="nav-buffer">Buffer</a></li> 282<li><a href="addons.html" class="nav-addons">C++ addons</a></li> 283<li><a href="n-api.html" class="nav-n-api">C/C++ 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class="nav-https-github-com-nodejs-node">Code repository and issue tracker</a></li> 342</ul></div> 343 </li> 344 345 346 <li class="picker-header"> 347 <a href="#"> 348 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 349 Other versions 350 </a> 351 <div class="picker"><ol id="alt-docs"><li><a href="https://nodejs.org/docs/latest-v20.x/api/perf_hooks.html">20.x</a></li> 352<li><a href="https://nodejs.org/docs/latest-v19.x/api/perf_hooks.html">19.x</a></li> 353<li><a href="https://nodejs.org/docs/latest-v18.x/api/perf_hooks.html">18.x <b>LTS</b></a></li> 354<li><a href="https://nodejs.org/docs/latest-v17.x/api/perf_hooks.html">17.x</a></li> 355<li><a href="https://nodejs.org/docs/latest-v16.x/api/perf_hooks.html">16.x</a></li> 356<li><a href="https://nodejs.org/docs/latest-v15.x/api/perf_hooks.html">15.x</a></li> 357<li><a href="https://nodejs.org/docs/latest-v14.x/api/perf_hooks.html">14.x</a></li> 358<li><a href="https://nodejs.org/docs/latest-v13.x/api/perf_hooks.html">13.x</a></li> 359<li><a href="https://nodejs.org/docs/latest-v12.x/api/perf_hooks.html">12.x</a></li> 360<li><a href="https://nodejs.org/docs/latest-v11.x/api/perf_hooks.html">11.x</a></li> 361<li><a href="https://nodejs.org/docs/latest-v10.x/api/perf_hooks.html">10.x</a></li> 362<li><a href="https://nodejs.org/docs/latest-v9.x/api/perf_hooks.html">9.x</a></li> 363<li><a href="https://nodejs.org/docs/latest-v8.x/api/perf_hooks.html">8.x</a></li></ol></div> 364 </li> 365 366 <li class="picker-header"> 367 <a href="#"> 368 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 369 Options 370 </a> 371 372 <div class="picker"> 373 <ul> 374 <li> 375 <a href="all.html">View on single page</a> 376 </li> 377 <li> 378 <a href="perf_hooks.json">View as JSON</a> 379 </li> 380 <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/main/doc/api/perf_hooks.md">Edit on GitHub</a></li> 381 </ul> 382 </div> 383 </li> 384 </ul> 385 </div> 386 <hr> 387 </header> 388 389 <details id="toc" open><summary>Table of contents</summary><ul> 390<li><span class="stability_2"><a href="#performance-measurement-apis">Performance measurement APIs</a></span> 391<ul> 392<li><a href="#perf_hooksperformance"><code>perf_hooks.performance</code></a> 393<ul> 394<li><a href="#performanceclearmarksname"><code>performance.clearMarks([name])</code></a></li> 395<li><a href="#performanceclearmeasuresname"><code>performance.clearMeasures([name])</code></a></li> 396<li><a href="#performanceclearresourcetimingsname"><code>performance.clearResourceTimings([name])</code></a></li> 397<li><a href="#performanceeventlooputilizationutilization1-utilization2"><code>performance.eventLoopUtilization([utilization1[, utilization2]])</code></a></li> 398<li><a href="#performancegetentries"><code>performance.getEntries()</code></a></li> 399<li><a href="#performancegetentriesbynamename-type"><code>performance.getEntriesByName(name[, type])</code></a></li> 400<li><a href="#performancegetentriesbytypetype"><code>performance.getEntriesByType(type)</code></a></li> 401<li><a href="#performancemarkname-options"><code>performance.mark([name[, options]])</code></a></li> 402<li><a href="#performancemarkresourcetimingtiminginfo-requestedurl-initiatortype-global-cachemode"><code>performance.markResourceTiming(timingInfo, requestedUrl, initiatorType, global, cacheMode)</code></a></li> 403<li><a href="#performancemeasurename-startmarkoroptions-endmark"><code>performance.measure(name[, startMarkOrOptions[, endMark]])</code></a></li> 404<li><a href="#performancenodetiming"><code>performance.nodeTiming</code></a></li> 405<li><a href="#performancenow"><code>performance.now()</code></a></li> 406<li><a href="#performancesetresourcetimingbuffersizemaxsize"><code>performance.setResourceTimingBufferSize(maxSize)</code></a></li> 407<li><a href="#performancetimeorigin"><code>performance.timeOrigin</code></a></li> 408<li><a href="#performancetimerifyfn-options"><code>performance.timerify(fn[, options])</code></a></li> 409<li><a href="#performancetojson"><code>performance.toJSON()</code></a> 410<ul> 411<li><a href="#event-resourcetimingbufferfull">Event: <code>'resourcetimingbufferfull'</code></a></li> 412</ul> 413</li> 414</ul> 415</li> 416<li><a href="#class-performanceentry">Class: <code>PerformanceEntry</code></a> 417<ul> 418<li><a href="#performanceentrydetail"><code>performanceEntry.detail</code></a></li> 419<li><a href="#performanceentryduration"><code>performanceEntry.duration</code></a></li> 420<li><a href="#performanceentryentrytype"><code>performanceEntry.entryType</code></a></li> 421<li><a href="#performanceentryflags"><code>performanceEntry.flags</code></a></li> 422<li><a href="#performanceentryname"><code>performanceEntry.name</code></a></li> 423<li><a href="#performanceentrykind"><code>performanceEntry.kind</code></a></li> 424<li><a href="#performanceentrystarttime"><code>performanceEntry.startTime</code></a></li> 425<li><a href="#garbage-collection-gc-details">Garbage Collection ('gc') Details</a></li> 426<li><a href="#http-http-details">HTTP ('http') Details</a></li> 427<li><a href="#http2-http2-details">HTTP/2 ('http2') Details</a></li> 428<li><a href="#timerify-function-details">Timerify ('function') Details</a></li> 429<li><a href="#net-net-details">Net ('net') Details</a></li> 430<li><a href="#dns-dns-details">DNS ('dns') Details</a></li> 431</ul> 432</li> 433<li><a href="#class-performancenodetiming">Class: <code>PerformanceNodeTiming</code></a> 434<ul> 435<li><a href="#performancenodetimingbootstrapcomplete"><code>performanceNodeTiming.bootstrapComplete</code></a></li> 436<li><a href="#performancenodetimingenvironment"><code>performanceNodeTiming.environment</code></a></li> 437<li><a href="#performancenodetimingidletime"><code>performanceNodeTiming.idleTime</code></a></li> 438<li><a href="#performancenodetimingloopexit"><code>performanceNodeTiming.loopExit</code></a></li> 439<li><a href="#performancenodetimingloopstart"><code>performanceNodeTiming.loopStart</code></a></li> 440<li><a href="#performancenodetimingnodestart"><code>performanceNodeTiming.nodeStart</code></a></li> 441<li><a href="#performancenodetimingv8start"><code>performanceNodeTiming.v8Start</code></a></li> 442</ul> 443</li> 444<li><a href="#class-performanceresourcetiming">Class: <code>PerformanceResourceTiming</code></a> 445<ul> 446<li><a href="#performanceresourcetimingworkerstart"><code>performanceResourceTiming.workerStart</code></a></li> 447<li><a href="#performanceresourcetimingredirectstart"><code>performanceResourceTiming.redirectStart</code></a></li> 448<li><a href="#performanceresourcetimingredirectend"><code>performanceResourceTiming.redirectEnd</code></a></li> 449<li><a href="#performanceresourcetimingfetchstart"><code>performanceResourceTiming.fetchStart</code></a></li> 450<li><a href="#performanceresourcetimingdomainlookupstart"><code>performanceResourceTiming.domainLookupStart</code></a></li> 451<li><a href="#performanceresourcetimingdomainlookupend"><code>performanceResourceTiming.domainLookupEnd</code></a></li> 452<li><a href="#performanceresourcetimingconnectstart"><code>performanceResourceTiming.connectStart</code></a></li> 453<li><a href="#performanceresourcetimingconnectend"><code>performanceResourceTiming.connectEnd</code></a></li> 454<li><a href="#performanceresourcetimingsecureconnectionstart"><code>performanceResourceTiming.secureConnectionStart</code></a></li> 455<li><a href="#performanceresourcetimingrequeststart"><code>performanceResourceTiming.requestStart</code></a></li> 456<li><a href="#performanceresourcetimingresponseend"><code>performanceResourceTiming.responseEnd</code></a></li> 457<li><a href="#performanceresourcetimingtransfersize"><code>performanceResourceTiming.transferSize</code></a></li> 458<li><a href="#performanceresourcetimingencodedbodysize"><code>performanceResourceTiming.encodedBodySize</code></a></li> 459<li><a href="#performanceresourcetimingdecodedbodysize"><code>performanceResourceTiming.decodedBodySize</code></a></li> 460<li><a href="#performanceresourcetimingtojson"><code>performanceResourceTiming.toJSON()</code></a></li> 461</ul> 462</li> 463<li><a href="#class-perf_hooksperformanceobserver">Class: <code>perf_hooks.PerformanceObserver</code></a> 464<ul> 465<li><a href="#performanceobserversupportedentrytypes"><code>PerformanceObserver.supportedEntryTypes</code></a></li> 466<li><a href="#new-performanceobservercallback"><code>new PerformanceObserver(callback)</code></a></li> 467<li><a href="#performanceobserverdisconnect"><code>performanceObserver.disconnect()</code></a></li> 468<li><a href="#performanceobserverobserveoptions"><code>performanceObserver.observe(options)</code></a></li> 469</ul> 470</li> 471<li><a href="#class-performanceobserverentrylist">Class: <code>PerformanceObserverEntryList</code></a> 472<ul> 473<li><a href="#performanceobserverentrylistgetentries"><code>performanceObserverEntryList.getEntries()</code></a></li> 474<li><a href="#performanceobserverentrylistgetentriesbynamename-type"><code>performanceObserverEntryList.getEntriesByName(name[, type])</code></a></li> 475<li><a href="#performanceobserverentrylistgetentriesbytypetype"><code>performanceObserverEntryList.getEntriesByType(type)</code></a></li> 476</ul> 477</li> 478<li><a href="#perf_hookscreatehistogramoptions"><code>perf_hooks.createHistogram([options])</code></a></li> 479<li><a href="#perf_hooksmonitoreventloopdelayoptions"><code>perf_hooks.monitorEventLoopDelay([options])</code></a></li> 480<li><a href="#class-histogram">Class: <code>Histogram</code></a> 481<ul> 482<li><a href="#histogramcount"><code>histogram.count</code></a></li> 483<li><a href="#histogramcountbigint"><code>histogram.countBigInt</code></a></li> 484<li><a href="#histogramexceeds"><code>histogram.exceeds</code></a></li> 485<li><a href="#histogramexceedsbigint"><code>histogram.exceedsBigInt</code></a></li> 486<li><a href="#histogrammax"><code>histogram.max</code></a></li> 487<li><a href="#histogrammaxbigint"><code>histogram.maxBigInt</code></a></li> 488<li><a href="#histogrammean"><code>histogram.mean</code></a></li> 489<li><a href="#histogrammin"><code>histogram.min</code></a></li> 490<li><a href="#histogramminbigint"><code>histogram.minBigInt</code></a></li> 491<li><a href="#histogrampercentilepercentile"><code>histogram.percentile(percentile)</code></a></li> 492<li><a href="#histogrampercentilebigintpercentile"><code>histogram.percentileBigInt(percentile)</code></a></li> 493<li><a href="#histogrampercentiles"><code>histogram.percentiles</code></a></li> 494<li><a href="#histogrampercentilesbigint"><code>histogram.percentilesBigInt</code></a></li> 495<li><a href="#histogramreset"><code>histogram.reset()</code></a></li> 496<li><a href="#histogramstddev"><code>histogram.stddev</code></a></li> 497</ul> 498</li> 499<li><a href="#class-intervalhistogram-extends-histogram">Class: <code>IntervalHistogram extends Histogram</code></a> 500<ul> 501<li><a href="#histogramdisable"><code>histogram.disable()</code></a></li> 502<li><a href="#histogramenable"><code>histogram.enable()</code></a></li> 503<li><a href="#cloning-an-intervalhistogram">Cloning an <code>IntervalHistogram</code></a></li> 504</ul> 505</li> 506<li><a href="#class-recordablehistogram-extends-histogram">Class: <code>RecordableHistogram extends Histogram</code></a> 507<ul> 508<li><a href="#histogramaddother"><code>histogram.add(other)</code></a></li> 509<li><a href="#histogramrecordval"><code>histogram.record(val)</code></a></li> 510<li><a href="#histogramrecorddelta"><code>histogram.recordDelta()</code></a></li> 511</ul> 512</li> 513<li><a href="#examples">Examples</a> 514<ul> 515<li><a href="#measuring-the-duration-of-async-operations">Measuring the duration of async operations</a></li> 516<li><a href="#measuring-how-long-it-takes-to-load-dependencies">Measuring how long it takes to load dependencies</a></li> 517<li><a href="#measuring-how-long-one-http-round-trip-takes">Measuring how long one HTTP round-trip takes</a></li> 518<li><a href="#measuring-how-long-the-netconnect-only-for-tcp-takes-when-the-connection-is-successful">Measuring how long the <code>net.connect</code> (only for TCP) takes when the connection is successful</a></li> 519<li><a href="#measuring-how-long-the-dns-takes-when-the-request-is-successful">Measuring how long the DNS takes when the request is successful</a></li> 520</ul> 521</li> 522</ul> 523</li> 524</ul></details> 525 526 <div id="apicontent"> 527 <h2>Performance measurement APIs<span><a class="mark" href="#performance-measurement-apis" id="performance-measurement-apis">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performance_measurement_apis"></a></h2> 528 529<p></p><div class="api_stability api_stability_2"><a href="documentation.html#stability-index">Stability: 2</a> - Stable</div><p></p> 530<p><strong>Source Code:</strong> <a href="https://github.com/nodejs/node/blob/v18.18.2/lib/perf_hooks.js">lib/perf_hooks.js</a></p> 531<p>This module provides an implementation of a subset of the W3C 532<a href="https://w3c.github.io/perf-timing-primer/">Web Performance APIs</a> as well as additional APIs for 533Node.js-specific performance measurements.</p> 534<p>Node.js supports the following <a href="https://w3c.github.io/perf-timing-primer/">Web Performance APIs</a>:</p> 535<ul> 536<li><a href="https://www.w3.org/TR/hr-time-2">High Resolution Time</a></li> 537<li><a href="https://w3c.github.io/performance-timeline/">Performance Timeline</a></li> 538<li><a href="https://www.w3.org/TR/user-timing/">User Timing</a></li> 539<li><a href="https://www.w3.org/TR/resource-timing-2/">Resource Timing</a></li> 540</ul> 541<pre><code class="language-js"><span class="hljs-keyword">const</span> { <span class="hljs-title class_">PerformanceObserver</span>, performance } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:perf_hooks'</span>); 542 543<span class="hljs-keyword">const</span> obs = <span class="hljs-keyword">new</span> <span class="hljs-title class_">PerformanceObserver</span>(<span class="hljs-function">(<span class="hljs-params">items</span>) =></span> { 544 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(items.<span class="hljs-title function_">getEntries</span>()[<span class="hljs-number">0</span>].<span class="hljs-property">duration</span>); 545 performance.<span class="hljs-title function_">clearMarks</span>(); 546}); 547obs.<span class="hljs-title function_">observe</span>({ <span class="hljs-attr">type</span>: <span class="hljs-string">'measure'</span> }); 548performance.<span class="hljs-title function_">measure</span>(<span class="hljs-string">'Start to Now'</span>); 549 550performance.<span class="hljs-title function_">mark</span>(<span class="hljs-string">'A'</span>); 551<span class="hljs-title function_">doSomeLongRunningProcess</span>(<span class="hljs-function">() =></span> { 552 performance.<span class="hljs-title function_">measure</span>(<span class="hljs-string">'A to Now'</span>, <span class="hljs-string">'A'</span>); 553 554 performance.<span class="hljs-title function_">mark</span>(<span class="hljs-string">'B'</span>); 555 performance.<span class="hljs-title function_">measure</span>(<span class="hljs-string">'A to B'</span>, <span class="hljs-string">'A'</span>, <span class="hljs-string">'B'</span>); 556});</code> <button class="copy-button">copy</button></pre> 557<section><h3><code>perf_hooks.performance</code><span><a class="mark" href="#perf_hooksperformance" id="perf_hooksperformance">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_perf_hooks_performance"></a></h3> 558<div class="api_metadata"> 559<span>Added in: v8.5.0</span> 560</div> 561<p>An object that can be used to collect performance metrics from the current 562Node.js instance. It is similar to <a href="https://developer.mozilla.org/en-US/docs/Web/API/Window/performance"><code>window.performance</code></a> in browsers.</p> 563<h4><code>performance.clearMarks([name])</code><span><a class="mark" href="#performanceclearmarksname" id="performanceclearmarksname">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performance_clearmarks_name"></a></h4> 564<div class="api_metadata"> 565<span>Added in: v8.5.0</span> 566</div> 567<ul> 568<li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 569</ul> 570<p>If <code>name</code> is not provided, removes all <code>PerformanceMark</code> objects from the 571Performance Timeline. If <code>name</code> is provided, removes only the named mark.</p> 572<h4><code>performance.clearMeasures([name])</code><span><a class="mark" href="#performanceclearmeasuresname" id="performanceclearmeasuresname">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performance_clearmeasures_name"></a></h4> 573<div class="api_metadata"> 574<span>Added in: v16.7.0</span> 575</div> 576<ul> 577<li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 578</ul> 579<p>If <code>name</code> is not provided, removes all <code>PerformanceMeasure</code> objects from the 580Performance Timeline. If <code>name</code> is provided, removes only the named measure.</p> 581<h4><code>performance.clearResourceTimings([name])</code><span><a class="mark" href="#performanceclearresourcetimingsname" id="performanceclearresourcetimingsname">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performance_clearresourcetimings_name"></a></h4> 582<div class="api_metadata"> 583<span>Added in: v18.2.0</span> 584</div> 585<ul> 586<li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 587</ul> 588<p>If <code>name</code> is not provided, removes all <code>PerformanceResourceTiming</code> objects from 589the Resource Timeline. If <code>name</code> is provided, removes only the named resource.</p> 590<h4><code>performance.eventLoopUtilization([utilization1[, utilization2]])</code><span><a class="mark" href="#performanceeventlooputilizationutilization1-utilization2" id="performanceeventlooputilizationutilization1-utilization2">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performance_eventlooputilization_utilization1_utilization2"></a></h4> 591<div class="api_metadata"> 592<span>Added in: v14.10.0, v12.19.0</span> 593</div> 594<ul> 595<li><code>utilization1</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> The result of a previous call to 596<code>eventLoopUtilization()</code>.</li> 597<li><code>utilization2</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> The result of a previous call to 598<code>eventLoopUtilization()</code> prior to <code>utilization1</code>.</li> 599<li>Returns <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 600<ul> 601<li><code>idle</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 602<li><code>active</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 603<li><code>utilization</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 604</ul> 605</li> 606</ul> 607<p>The <code>eventLoopUtilization()</code> method returns an object that contains the 608cumulative duration of time the event loop has been both idle and active as a 609high resolution milliseconds timer. The <code>utilization</code> value is the calculated 610Event Loop Utilization (ELU).</p> 611<p>If bootstrapping has not yet finished on the main thread the properties have 612the value of <code>0</code>. The ELU is immediately available on <a href="worker_threads.html#worker-threads">Worker threads</a> since 613bootstrap happens within the event loop.</p> 614<p>Both <code>utilization1</code> and <code>utilization2</code> are optional parameters.</p> 615<p>If <code>utilization1</code> is passed, then the delta between the current call's <code>active</code> 616and <code>idle</code> times, as well as the corresponding <code>utilization</code> value are 617calculated and returned (similar to <a href="process.html#processhrtimetime"><code>process.hrtime()</code></a>).</p> 618<p>If <code>utilization1</code> and <code>utilization2</code> are both passed, then the delta is 619calculated between the two arguments. This is a convenience option because, 620unlike <a href="process.html#processhrtimetime"><code>process.hrtime()</code></a>, calculating the ELU is more complex than a 621single subtraction.</p> 622<p>ELU is similar to CPU utilization, except that it only measures event loop 623statistics and not CPU usage. It represents the percentage of time the event 624loop has spent outside the event loop's event provider (e.g. <code>epoll_wait</code>). 625No other CPU idle time is taken into consideration. The following is an example 626of how a mostly idle process will have a high ELU.</p> 627<pre><code class="language-js"><span class="hljs-meta">'use strict'</span>; 628<span class="hljs-keyword">const</span> { eventLoopUtilization } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:perf_hooks'</span>).<span class="hljs-property">performance</span>; 629<span class="hljs-keyword">const</span> { spawnSync } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:child_process'</span>); 630 631<span class="hljs-title function_">setImmediate</span>(<span class="hljs-function">() =></span> { 632 <span class="hljs-keyword">const</span> elu = <span class="hljs-title function_">eventLoopUtilization</span>(); 633 <span class="hljs-title function_">spawnSync</span>(<span class="hljs-string">'sleep'</span>, [<span class="hljs-string">'5'</span>]); 634 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-title function_">eventLoopUtilization</span>(elu).<span class="hljs-property">utilization</span>); 635});</code> <button class="copy-button">copy</button></pre> 636<p>Although the CPU is mostly idle while running this script, the value of 637<code>utilization</code> is <code>1</code>. This is because the call to 638<a href="child_process.html#child_processspawnsynccommand-args-options"><code>child_process.spawnSync()</code></a> blocks the event loop from proceeding.</p> 639<p>Passing in a user-defined object instead of the result of a previous call to 640<code>eventLoopUtilization()</code> will lead to undefined behavior. The return values 641are not guaranteed to reflect any correct state of the event loop.</p> 642<h4><code>performance.getEntries()</code><span><a class="mark" href="#performancegetentries" id="performancegetentries">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performance_getentries"></a></h4> 643<div class="api_metadata"> 644<span>Added in: v16.7.0</span> 645</div> 646<ul> 647<li>Returns: <a href="perf_hooks.html#class-performanceentry" class="type"><PerformanceEntry[]></a></li> 648</ul> 649<p>Returns a list of <code>PerformanceEntry</code> objects in chronological order with 650respect to <code>performanceEntry.startTime</code>. If you are only interested in 651performance entries of certain types or that have certain names, see 652<code>performance.getEntriesByType()</code> and <code>performance.getEntriesByName()</code>.</p> 653<h4><code>performance.getEntriesByName(name[, type])</code><span><a class="mark" href="#performancegetentriesbynamename-type" id="performancegetentriesbynamename-type">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performance_getentriesbyname_name_type"></a></h4> 654<div class="api_metadata"> 655<span>Added in: v16.7.0</span> 656</div> 657<ul> 658<li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 659<li><code>type</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 660<li>Returns: <a href="perf_hooks.html#class-performanceentry" class="type"><PerformanceEntry[]></a></li> 661</ul> 662<p>Returns a list of <code>PerformanceEntry</code> objects in chronological order 663with respect to <code>performanceEntry.startTime</code> whose <code>performanceEntry.name</code> is 664equal to <code>name</code>, and optionally, whose <code>performanceEntry.entryType</code> is equal to 665<code>type</code>.</p> 666<h4><code>performance.getEntriesByType(type)</code><span><a class="mark" href="#performancegetentriesbytypetype" id="performancegetentriesbytypetype">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performance_getentriesbytype_type"></a></h4> 667<div class="api_metadata"> 668<span>Added in: v16.7.0</span> 669</div> 670<ul> 671<li><code>type</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 672<li>Returns: <a href="perf_hooks.html#class-performanceentry" class="type"><PerformanceEntry[]></a></li> 673</ul> 674<p>Returns a list of <code>PerformanceEntry</code> objects in chronological order 675with respect to <code>performanceEntry.startTime</code> whose <code>performanceEntry.entryType</code> 676is equal to <code>type</code>.</p> 677<h4><code>performance.mark([name[, options]])</code><span><a class="mark" href="#performancemarkname-options" id="performancemarkname-options">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performance_mark_name_options"></a></h4> 678<div class="api_metadata"> 679<details class="changelog"><summary>History</summary> 680<table> 681<tbody><tr><th>Version</th><th>Changes</th></tr> 682<tr><td>v16.0.0</td> 683<td><p>Updated to conform to the User Timing Level 3 specification.</p></td></tr> 684<tr><td>v8.5.0</td> 685<td><p><span>Added in: v8.5.0</span></p></td></tr> 686</tbody></table> 687</details> 688</div> 689<ul> 690<li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 691<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 692<ul> 693<li><code>detail</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> Additional optional detail to include with the mark.</li> 694<li><code>startTime</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> An optional timestamp to be used as the mark time. 695<strong>Default</strong>: <code>performance.now()</code>.</li> 696</ul> 697</li> 698</ul> 699<p>Creates a new <code>PerformanceMark</code> entry in the Performance Timeline. A 700<code>PerformanceMark</code> is a subclass of <code>PerformanceEntry</code> whose 701<code>performanceEntry.entryType</code> is always <code>'mark'</code>, and whose 702<code>performanceEntry.duration</code> is always <code>0</code>. Performance marks are used 703to mark specific significant moments in the Performance Timeline.</p> 704<p>The created <code>PerformanceMark</code> entry is put in the global Performance Timeline 705and can be queried with <code>performance.getEntries</code>, 706<code>performance.getEntriesByName</code>, and <code>performance.getEntriesByType</code>. When the 707observation is performed, the entries should be cleared from the global 708Performance Timeline manually with <code>performance.clearMarks</code>.</p> 709<h4><code>performance.markResourceTiming(timingInfo, requestedUrl, initiatorType, global, cacheMode)</code><span><a class="mark" href="#performancemarkresourcetimingtiminginfo-requestedurl-initiatortype-global-cachemode" id="performancemarkresourcetimingtiminginfo-requestedurl-initiatortype-global-cachemode">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performance_markresourcetiming_timinginfo_requestedurl_initiatortype_global_cachemode"></a></h4> 710<div class="api_metadata"> 711<span>Added in: v18.2.0</span> 712</div> 713<ul> 714<li><code>timingInfo</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> <a href="https://fetch.spec.whatwg.org/#fetch-timing-info">Fetch Timing Info</a></li> 715<li><code>requestedUrl</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The resource url</li> 716<li><code>initiatorType</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The initiator name, e.g: 'fetch'</li> 717<li><code>global</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> 718<li><code>cacheMode</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The cache mode must be an empty string ('') or 'local'</li> 719</ul> 720<p><em>This property is an extension by Node.js. It is not available in Web browsers.</em></p> 721<p>Creates a new <code>PerformanceResourceTiming</code> entry in the Resource Timeline. A 722<code>PerformanceResourceTiming</code> is a subclass of <code>PerformanceEntry</code> whose 723<code>performanceEntry.entryType</code> is always <code>'resource'</code>. Performance resources 724are used to mark moments in the Resource Timeline.</p> 725<p>The created <code>PerformanceMark</code> entry is put in the global Resource Timeline 726and can be queried with <code>performance.getEntries</code>, 727<code>performance.getEntriesByName</code>, and <code>performance.getEntriesByType</code>. When the 728observation is performed, the entries should be cleared from the global 729Performance Timeline manually with <code>performance.clearResourceTimings</code>.</p> 730<h4><code>performance.measure(name[, startMarkOrOptions[, endMark]])</code><span><a class="mark" href="#performancemeasurename-startmarkoroptions-endmark" id="performancemeasurename-startmarkoroptions-endmark">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performance_measure_name_startmarkoroptions_endmark"></a></h4> 731<div class="api_metadata"> 732<details class="changelog"><summary>History</summary> 733<table> 734<tbody><tr><th>Version</th><th>Changes</th></tr> 735<tr><td>v16.0.0</td> 736<td><p>Updated to conform to the User Timing Level 3 specification.</p></td></tr> 737<tr><td>v13.13.0, v12.16.3</td> 738<td><p>Make <code>startMark</code> and <code>endMark</code> parameters optional.</p></td></tr> 739<tr><td>v8.5.0</td> 740<td><p><span>Added in: v8.5.0</span></p></td></tr> 741</tbody></table> 742</details> 743</div> 744<ul> 745<li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 746<li><code>startMarkOrOptions</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> Optional. 747<ul> 748<li><code>detail</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> Additional optional detail to include with the measure.</li> 749<li><code>duration</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Duration between start and end times.</li> 750<li><code>end</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Timestamp to be used as the end time, or a string 751identifying a previously recorded mark.</li> 752<li><code>start</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Timestamp to be used as the start time, or a string 753identifying a previously recorded mark.</li> 754</ul> 755</li> 756<li><code>endMark</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Optional. Must be omitted if <code>startMarkOrOptions</code> is an 757<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a>.</li> 758</ul> 759<p>Creates a new <code>PerformanceMeasure</code> entry in the Performance Timeline. A 760<code>PerformanceMeasure</code> is a subclass of <code>PerformanceEntry</code> whose 761<code>performanceEntry.entryType</code> is always <code>'measure'</code>, and whose 762<code>performanceEntry.duration</code> measures the number of milliseconds elapsed since 763<code>startMark</code> and <code>endMark</code>.</p> 764<p>The <code>startMark</code> argument may identify any <em>existing</em> <code>PerformanceMark</code> in the 765Performance Timeline, or <em>may</em> identify any of the timestamp properties 766provided by the <code>PerformanceNodeTiming</code> class. If the named <code>startMark</code> does 767not exist, an error is thrown.</p> 768<p>The optional <code>endMark</code> argument must identify any <em>existing</em> <code>PerformanceMark</code> 769in the Performance Timeline or any of the timestamp properties provided by the 770<code>PerformanceNodeTiming</code> class. <code>endMark</code> will be <code>performance.now()</code> 771if no parameter is passed, otherwise if the named <code>endMark</code> does not exist, an 772error will be thrown.</p> 773<p>The created <code>PerformanceMeasure</code> entry is put in the global Performance Timeline 774and can be queried with <code>performance.getEntries</code>, 775<code>performance.getEntriesByName</code>, and <code>performance.getEntriesByType</code>. When the 776observation is performed, the entries should be cleared from the global 777Performance Timeline manually with <code>performance.clearMeasures</code>.</p> 778<h4><code>performance.nodeTiming</code><span><a class="mark" href="#performancenodetiming" id="performancenodetiming">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performance_nodetiming"></a></h4> 779<div class="api_metadata"> 780<span>Added in: v8.5.0</span> 781</div> 782<ul> 783<li><a href="perf_hooks.html#class-performancenodetiming" class="type"><PerformanceNodeTiming></a></li> 784</ul> 785<p><em>This property is an extension by Node.js. It is not available in Web browsers.</em></p> 786<p>An instance of the <code>PerformanceNodeTiming</code> class that provides performance 787metrics for specific Node.js operational milestones.</p> 788<h4><code>performance.now()</code><span><a class="mark" href="#performancenow" id="performancenow">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performance_now"></a></h4> 789<div class="api_metadata"> 790<span>Added in: v8.5.0</span> 791</div> 792<ul> 793<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 794</ul> 795<p>Returns the current high resolution millisecond timestamp, where 0 represents 796the start of the current <code>node</code> process.</p> 797<h4><code>performance.setResourceTimingBufferSize(maxSize)</code><span><a class="mark" href="#performancesetresourcetimingbuffersizemaxsize" id="performancesetresourcetimingbuffersizemaxsize">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performance_setresourcetimingbuffersize_maxsize"></a></h4> 798<div class="api_metadata"> 799<span>Added in: v18.8.0</span> 800</div> 801<p>Sets the global performance resource timing buffer size to the specified number 802of "resource" type performance entry objects.</p> 803<p>By default the max buffer size is set to 250.</p> 804<h4><code>performance.timeOrigin</code><span><a class="mark" href="#performancetimeorigin" id="performancetimeorigin">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performance_timeorigin"></a></h4> 805<div class="api_metadata"> 806<span>Added in: v8.5.0</span> 807</div> 808<ul> 809<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 810</ul> 811<p>The <a href="https://w3c.github.io/hr-time/#dom-performance-timeorigin"><code>timeOrigin</code></a> specifies the high resolution millisecond timestamp at 812which the current <code>node</code> process began, measured in Unix time.</p> 813<h4><code>performance.timerify(fn[, options])</code><span><a class="mark" href="#performancetimerifyfn-options" id="performancetimerifyfn-options">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performance_timerify_fn_options"></a></h4> 814<div class="api_metadata"> 815<details class="changelog"><summary>History</summary> 816<table> 817<tbody><tr><th>Version</th><th>Changes</th></tr> 818<tr><td>v16.0.0</td> 819<td><p>Added the histogram option.</p></td></tr> 820<tr><td>v16.0.0</td> 821<td><p>Re-implemented to use pure-JavaScript and the ability to time async functions.</p></td></tr> 822<tr><td>v8.5.0</td> 823<td><p><span>Added in: v8.5.0</span></p></td></tr> 824</tbody></table> 825</details> 826</div> 827<ul> 828<li><code>fn</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a></li> 829<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 830<ul> 831<li><code>histogram</code> <a href="perf_hooks.html#class-recordablehistogram-extends-histogram" class="type"><RecordableHistogram></a> A histogram object created using 832<code>perf_hooks.createHistogram()</code> that will record runtime durations in 833nanoseconds.</li> 834</ul> 835</li> 836</ul> 837<p><em>This property is an extension by Node.js. It is not available in Web browsers.</em></p> 838<p>Wraps a function within a new function that measures the running time of the 839wrapped function. A <code>PerformanceObserver</code> must be subscribed to the <code>'function'</code> 840event type in order for the timing details to be accessed.</p> 841<pre><code class="language-js"><span class="hljs-keyword">const</span> { 842 performance, 843 <span class="hljs-title class_">PerformanceObserver</span>, 844} = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:perf_hooks'</span>); 845 846<span class="hljs-keyword">function</span> <span class="hljs-title function_">someFunction</span>(<span class="hljs-params"></span>) { 847 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">'hello world'</span>); 848} 849 850<span class="hljs-keyword">const</span> wrapped = performance.<span class="hljs-title function_">timerify</span>(someFunction); 851 852<span class="hljs-keyword">const</span> obs = <span class="hljs-keyword">new</span> <span class="hljs-title class_">PerformanceObserver</span>(<span class="hljs-function">(<span class="hljs-params">list</span>) =></span> { 853 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(list.<span class="hljs-title function_">getEntries</span>()[<span class="hljs-number">0</span>].<span class="hljs-property">duration</span>); 854 855 performance.<span class="hljs-title function_">clearMarks</span>(); 856 performance.<span class="hljs-title function_">clearMeasures</span>(); 857 obs.<span class="hljs-title function_">disconnect</span>(); 858}); 859obs.<span class="hljs-title function_">observe</span>({ <span class="hljs-attr">entryTypes</span>: [<span class="hljs-string">'function'</span>] }); 860 861<span class="hljs-comment">// A performance timeline entry will be created</span> 862<span class="hljs-title function_">wrapped</span>();</code> <button class="copy-button">copy</button></pre> 863<p>If the wrapped function returns a promise, a finally handler will be attached 864to the promise and the duration will be reported once the finally handler is 865invoked.</p> 866<h4><code>performance.toJSON()</code><span><a class="mark" href="#performancetojson" id="performancetojson">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performance_tojson"></a></h4> 867<div class="api_metadata"> 868<span>Added in: v16.1.0</span> 869</div> 870<p>An object which is JSON representation of the <code>performance</code> object. It 871is similar to <a href="https://developer.mozilla.org/en-US/docs/Web/API/Performance/toJSON"><code>window.performance.toJSON</code></a> in browsers.</p> 872<h5>Event: <code>'resourcetimingbufferfull'</code><span><a class="mark" href="#event-resourcetimingbufferfull" id="event-resourcetimingbufferfull">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_event_resourcetimingbufferfull"></a></h5> 873<div class="api_metadata"> 874<span>Added in: v18.8.0</span> 875</div> 876<p>The <code>'resourcetimingbufferfull'</code> event is fired when the global performance 877resource timing buffer is full. Adjust resource timing buffer size with 878<code>performance.setResourceTimingBufferSize()</code> or clear the buffer with 879<code>performance.clearResourceTimings()</code> in the event listener to allow 880more entries to be added to the performance timeline buffer.</p> 881</section><section><h3>Class: <code>PerformanceEntry</code><span><a class="mark" href="#class-performanceentry" id="class-performanceentry">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_class_performanceentry"></a></h3> 882<div class="api_metadata"> 883<span>Added in: v8.5.0</span> 884</div> 885<h4><code>performanceEntry.detail</code><span><a class="mark" href="#performanceentrydetail" id="performanceentrydetail">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceentry_detail"></a></h4> 886<div class="api_metadata"> 887<span>Added in: v16.0.0</span> 888</div> 889<ul> 890<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a></li> 891</ul> 892<p>Additional detail specific to the <code>entryType</code>.</p> 893<h4><code>performanceEntry.duration</code><span><a class="mark" href="#performanceentryduration" id="performanceentryduration">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceentry_duration"></a></h4> 894<div class="api_metadata"> 895<span>Added in: v8.5.0</span> 896</div> 897<ul> 898<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 899</ul> 900<p>The total number of milliseconds elapsed for this entry. This value will not 901be meaningful for all Performance Entry types.</p> 902<h4><code>performanceEntry.entryType</code><span><a class="mark" href="#performanceentryentrytype" id="performanceentryentrytype">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceentry_entrytype"></a></h4> 903<div class="api_metadata"> 904<span>Added in: v8.5.0</span> 905</div> 906<ul> 907<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 908</ul> 909<p>The type of the performance entry. It may be one of:</p> 910<ul> 911<li><code>'node'</code> (Node.js only)</li> 912<li><code>'mark'</code> (available on the Web)</li> 913<li><code>'measure'</code> (available on the Web)</li> 914<li><code>'gc'</code> (Node.js only)</li> 915<li><code>'function'</code> (Node.js only)</li> 916<li><code>'http2'</code> (Node.js only)</li> 917<li><code>'http'</code> (Node.js only)</li> 918</ul> 919<h4><code>performanceEntry.flags</code><span><a class="mark" href="#performanceentryflags" id="performanceentryflags">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceentry_flags"></a></h4> 920<div class="api_metadata"> 921<details class="changelog"><summary>History</summary> 922<table> 923<tbody><tr><th>Version</th><th>Changes</th></tr> 924<tr><td>v16.0.0</td> 925<td><p>Runtime deprecated. Now moved to the detail property when entryType is 'gc'.</p></td></tr> 926<tr><td>v13.9.0, v12.17.0</td> 927<td><p><span>Added in: v13.9.0, v12.17.0</span></p></td></tr> 928</tbody></table> 929</details> 930</div> 931<ul> 932<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 933</ul> 934<p><em>This property is an extension by Node.js. It is not available in Web browsers.</em></p> 935<p>When <code>performanceEntry.entryType</code> is equal to <code>'gc'</code>, the <code>performance.flags</code> 936property contains additional information about garbage collection operation. 937The value may be one of:</p> 938<ul> 939<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_NO</code></li> 940<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_CONSTRUCT_RETAINED</code></li> 941<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_FORCED</code></li> 942<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_SYNCHRONOUS_PHANTOM_PROCESSING</code></li> 943<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_ALL_AVAILABLE_GARBAGE</code></li> 944<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_ALL_EXTERNAL_MEMORY</code></li> 945<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_SCHEDULE_IDLE</code></li> 946</ul> 947<h4><code>performanceEntry.name</code><span><a class="mark" href="#performanceentryname" id="performanceentryname">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceentry_name"></a></h4> 948<div class="api_metadata"> 949<span>Added in: v8.5.0</span> 950</div> 951<ul> 952<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 953</ul> 954<p>The name of the performance entry.</p> 955<h4><code>performanceEntry.kind</code><span><a class="mark" href="#performanceentrykind" id="performanceentrykind">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceentry_kind"></a></h4> 956<div class="api_metadata"> 957<details class="changelog"><summary>History</summary> 958<table> 959<tbody><tr><th>Version</th><th>Changes</th></tr> 960<tr><td>v16.0.0</td> 961<td><p>Runtime deprecated. Now moved to the detail property when entryType is 'gc'.</p></td></tr> 962<tr><td>v8.5.0</td> 963<td><p><span>Added in: v8.5.0</span></p></td></tr> 964</tbody></table> 965</details> 966</div> 967<ul> 968<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 969</ul> 970<p><em>This property is an extension by Node.js. It is not available in Web browsers.</em></p> 971<p>When <code>performanceEntry.entryType</code> is equal to <code>'gc'</code>, the <code>performance.kind</code> 972property identifies the type of garbage collection operation that occurred. 973The value may be one of:</p> 974<ul> 975<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_MAJOR</code></li> 976<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_MINOR</code></li> 977<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_INCREMENTAL</code></li> 978<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_WEAKCB</code></li> 979</ul> 980<h4><code>performanceEntry.startTime</code><span><a class="mark" href="#performanceentrystarttime" id="performanceentrystarttime">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceentry_starttime"></a></h4> 981<div class="api_metadata"> 982<span>Added in: v8.5.0</span> 983</div> 984<ul> 985<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 986</ul> 987<p>The high resolution millisecond timestamp marking the starting time of the 988Performance Entry.</p> 989<h4>Garbage Collection ('gc') Details<span><a class="mark" href="#garbage-collection-gc-details" id="garbage-collection-gc-details">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_garbage_collection_gc_details"></a></h4> 990<p>When <code>performanceEntry.type</code> is equal to <code>'gc'</code>, the <code>performanceEntry.detail</code> 991property will be an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> with two properties:</p> 992<ul> 993<li><code>kind</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> One of: 994<ul> 995<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_MAJOR</code></li> 996<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_MINOR</code></li> 997<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_INCREMENTAL</code></li> 998<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_WEAKCB</code></li> 999</ul> 1000</li> 1001<li><code>flags</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> One of: 1002<ul> 1003<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_NO</code></li> 1004<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_CONSTRUCT_RETAINED</code></li> 1005<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_FORCED</code></li> 1006<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_SYNCHRONOUS_PHANTOM_PROCESSING</code></li> 1007<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_ALL_AVAILABLE_GARBAGE</code></li> 1008<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_ALL_EXTERNAL_MEMORY</code></li> 1009<li><code>perf_hooks.constants.NODE_PERFORMANCE_GC_FLAGS_SCHEDULE_IDLE</code></li> 1010</ul> 1011</li> 1012</ul> 1013<h4>HTTP ('http') Details<span><a class="mark" href="#http-http-details" id="http-http-details">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_http_http_details"></a></h4> 1014<p>When <code>performanceEntry.type</code> is equal to <code>'http'</code>, the <code>performanceEntry.detail</code> 1015property will be an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> containing additional information.</p> 1016<p>If <code>performanceEntry.name</code> is equal to <code>HttpClient</code>, the <code>detail</code> 1017will contain the following properties: <code>req</code>, <code>res</code>. And the <code>req</code> property 1018will be an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> containing <code>method</code>, <code>url</code>, <code>headers</code>, the <code>res</code> property 1019will be an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> containing <code>statusCode</code>, <code>statusMessage</code>, <code>headers</code>.</p> 1020<p>If <code>performanceEntry.name</code> is equal to <code>HttpRequest</code>, the <code>detail</code> 1021will contain the following properties: <code>req</code>, <code>res</code>. And the <code>req</code> property 1022will be an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> containing <code>method</code>, <code>url</code>, <code>headers</code>, the <code>res</code> property 1023will be an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> containing <code>statusCode</code>, <code>statusMessage</code>, <code>headers</code>.</p> 1024<p>This could add additional memory overhead and should only be used for 1025diagnostic purposes, not left turned on in production by default.</p> 1026<h4>HTTP/2 ('http2') Details<span><a class="mark" href="#http2-http2-details" id="http2-http2-details">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_http_2_http2_details"></a></h4> 1027<p>When <code>performanceEntry.type</code> is equal to <code>'http2'</code>, the 1028<code>performanceEntry.detail</code> property will be an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> containing 1029additional performance information.</p> 1030<p>If <code>performanceEntry.name</code> is equal to <code>Http2Stream</code>, the <code>detail</code> 1031will contain the following properties:</p> 1032<ul> 1033<li><code>bytesRead</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The number of <code>DATA</code> frame bytes received for this 1034<code>Http2Stream</code>.</li> 1035<li><code>bytesWritten</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The number of <code>DATA</code> frame bytes sent for this 1036<code>Http2Stream</code>.</li> 1037<li><code>id</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The identifier of the associated <code>Http2Stream</code></li> 1038<li><code>timeToFirstByte</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The number of milliseconds elapsed between the 1039<code>PerformanceEntry</code> <code>startTime</code> and the reception of the first <code>DATA</code> frame.</li> 1040<li><code>timeToFirstByteSent</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The number of milliseconds elapsed between 1041the <code>PerformanceEntry</code> <code>startTime</code> and sending of the first <code>DATA</code> frame.</li> 1042<li><code>timeToFirstHeader</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The number of milliseconds elapsed between the 1043<code>PerformanceEntry</code> <code>startTime</code> and the reception of the first header.</li> 1044</ul> 1045<p>If <code>performanceEntry.name</code> is equal to <code>Http2Session</code>, the <code>detail</code> will 1046contain the following properties:</p> 1047<ul> 1048<li><code>bytesRead</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The number of bytes received for this <code>Http2Session</code>.</li> 1049<li><code>bytesWritten</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The number of bytes sent for this <code>Http2Session</code>.</li> 1050<li><code>framesReceived</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The number of HTTP/2 frames received by the 1051<code>Http2Session</code>.</li> 1052<li><code>framesSent</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The number of HTTP/2 frames sent by the <code>Http2Session</code>.</li> 1053<li><code>maxConcurrentStreams</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The maximum number of streams concurrently 1054open during the lifetime of the <code>Http2Session</code>.</li> 1055<li><code>pingRTT</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The number of milliseconds elapsed since the transmission 1056of a <code>PING</code> frame and the reception of its acknowledgment. Only present if 1057a <code>PING</code> frame has been sent on the <code>Http2Session</code>.</li> 1058<li><code>streamAverageDuration</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The average duration (in milliseconds) for 1059all <code>Http2Stream</code> instances.</li> 1060<li><code>streamCount</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The number of <code>Http2Stream</code> instances processed by 1061the <code>Http2Session</code>.</li> 1062<li><code>type</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> Either <code>'server'</code> or <code>'client'</code> to identify the type of 1063<code>Http2Session</code>.</li> 1064</ul> 1065<h4>Timerify ('function') Details<span><a class="mark" href="#timerify-function-details" id="timerify-function-details">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_timerify_function_details"></a></h4> 1066<p>When <code>performanceEntry.type</code> is equal to <code>'function'</code>, the 1067<code>performanceEntry.detail</code> property will be an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array" class="type"><Array></a> listing 1068the input arguments to the timed function.</p> 1069<h4>Net ('net') Details<span><a class="mark" href="#net-net-details" id="net-net-details">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_net_net_details"></a></h4> 1070<p>When <code>performanceEntry.type</code> is equal to <code>'net'</code>, the 1071<code>performanceEntry.detail</code> property will be an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> containing 1072additional information.</p> 1073<p>If <code>performanceEntry.name</code> is equal to <code>connect</code>, the <code>detail</code> 1074will contain the following properties: <code>host</code>, <code>port</code>.</p> 1075<h4>DNS ('dns') Details<span><a class="mark" href="#dns-dns-details" id="dns-dns-details">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_dns_dns_details"></a></h4> 1076<p>When <code>performanceEntry.type</code> is equal to <code>'dns'</code>, the 1077<code>performanceEntry.detail</code> property will be an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> containing 1078additional information.</p> 1079<p>If <code>performanceEntry.name</code> is equal to <code>lookup</code>, the <code>detail</code> 1080will contain the following properties: <code>hostname</code>, <code>family</code>, <code>hints</code>, <code>verbatim</code>, 1081<code>addresses</code>.</p> 1082<p>If <code>performanceEntry.name</code> is equal to <code>lookupService</code>, the <code>detail</code> will 1083contain the following properties: <code>host</code>, <code>port</code>, <code>hostname</code>, <code>service</code>.</p> 1084<p>If <code>performanceEntry.name</code> is equal to <code>queryxxx</code> or <code>getHostByAddr</code>, the <code>detail</code> will 1085contain the following properties: <code>host</code>, <code>ttl</code>, <code>result</code>. The value of <code>result</code> is 1086same as the result of <code>queryxxx</code> or <code>getHostByAddr</code>.</p> 1087</section><section><h3>Class: <code>PerformanceNodeTiming</code><span><a class="mark" href="#class-performancenodetiming" id="class-performancenodetiming">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_class_performancenodetiming"></a></h3> 1088<div class="api_metadata"> 1089<span>Added in: v8.5.0</span> 1090</div> 1091<ul> 1092<li>Extends: <a href="perf_hooks.html#class-performanceentry" class="type"><PerformanceEntry></a></li> 1093</ul> 1094<p><em>This property is an extension by Node.js. It is not available in Web browsers.</em></p> 1095<p>Provides timing details for Node.js itself. The constructor of this class 1096is not exposed to users.</p> 1097<h4><code>performanceNodeTiming.bootstrapComplete</code><span><a class="mark" href="#performancenodetimingbootstrapcomplete" id="performancenodetimingbootstrapcomplete">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performancenodetiming_bootstrapcomplete"></a></h4> 1098<div class="api_metadata"> 1099<span>Added in: v8.5.0</span> 1100</div> 1101<ul> 1102<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1103</ul> 1104<p>The high resolution millisecond timestamp at which the Node.js process 1105completed bootstrapping. If bootstrapping has not yet finished, the property 1106has the value of -1.</p> 1107<h4><code>performanceNodeTiming.environment</code><span><a class="mark" href="#performancenodetimingenvironment" id="performancenodetimingenvironment">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performancenodetiming_environment"></a></h4> 1108<div class="api_metadata"> 1109<span>Added in: v8.5.0</span> 1110</div> 1111<ul> 1112<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1113</ul> 1114<p>The high resolution millisecond timestamp at which the Node.js environment was 1115initialized.</p> 1116<h4><code>performanceNodeTiming.idleTime</code><span><a class="mark" href="#performancenodetimingidletime" id="performancenodetimingidletime">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performancenodetiming_idletime"></a></h4> 1117<div class="api_metadata"> 1118<span>Added in: v14.10.0, v12.19.0</span> 1119</div> 1120<ul> 1121<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1122</ul> 1123<p>The high resolution millisecond timestamp of the amount of time the event loop 1124has been idle within the event loop's event provider (e.g. <code>epoll_wait</code>). This 1125does not take CPU usage into consideration. If the event loop has not yet 1126started (e.g., in the first tick of the main script), the property has the 1127value of 0.</p> 1128<h4><code>performanceNodeTiming.loopExit</code><span><a class="mark" href="#performancenodetimingloopexit" id="performancenodetimingloopexit">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performancenodetiming_loopexit"></a></h4> 1129<div class="api_metadata"> 1130<span>Added in: v8.5.0</span> 1131</div> 1132<ul> 1133<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1134</ul> 1135<p>The high resolution millisecond timestamp at which the Node.js event loop 1136exited. If the event loop has not yet exited, the property has the value of -1. 1137It can only have a value of not -1 in a handler of the <a href="process.html#event-exit"><code>'exit'</code></a> event.</p> 1138<h4><code>performanceNodeTiming.loopStart</code><span><a class="mark" href="#performancenodetimingloopstart" id="performancenodetimingloopstart">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performancenodetiming_loopstart"></a></h4> 1139<div class="api_metadata"> 1140<span>Added in: v8.5.0</span> 1141</div> 1142<ul> 1143<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1144</ul> 1145<p>The high resolution millisecond timestamp at which the Node.js event loop 1146started. If the event loop has not yet started (e.g., in the first tick of the 1147main script), the property has the value of -1.</p> 1148<h4><code>performanceNodeTiming.nodeStart</code><span><a class="mark" href="#performancenodetimingnodestart" id="performancenodetimingnodestart">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performancenodetiming_nodestart"></a></h4> 1149<div class="api_metadata"> 1150<span>Added in: v8.5.0</span> 1151</div> 1152<ul> 1153<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1154</ul> 1155<p>The high resolution millisecond timestamp at which the Node.js process was 1156initialized.</p> 1157<h4><code>performanceNodeTiming.v8Start</code><span><a class="mark" href="#performancenodetimingv8start" id="performancenodetimingv8start">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performancenodetiming_v8start"></a></h4> 1158<div class="api_metadata"> 1159<span>Added in: v8.5.0</span> 1160</div> 1161<ul> 1162<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1163</ul> 1164<p>The high resolution millisecond timestamp at which the V8 platform was 1165initialized.</p> 1166</section><section><h3>Class: <code>PerformanceResourceTiming</code><span><a class="mark" href="#class-performanceresourcetiming" id="class-performanceresourcetiming">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_class_performanceresourcetiming"></a></h3> 1167<div class="api_metadata"> 1168<span>Added in: v18.2.0</span> 1169</div> 1170<ul> 1171<li>Extends: <a href="perf_hooks.html#class-performanceentry" class="type"><PerformanceEntry></a></li> 1172</ul> 1173<p>Provides detailed network timing data regarding the loading of an application's 1174resources.</p> 1175<p>The constructor of this class is not exposed to users directly.</p> 1176<h4><code>performanceResourceTiming.workerStart</code><span><a class="mark" href="#performanceresourcetimingworkerstart" id="performanceresourcetimingworkerstart">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceresourcetiming_workerstart"></a></h4> 1177<div class="api_metadata"> 1178<span>Added in: v18.2.0</span> 1179</div> 1180<ul> 1181<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1182</ul> 1183<p>The high resolution millisecond timestamp at immediately before dispatching 1184the <code>fetch</code> request. If the resource is not intercepted by a worker the property 1185will always return 0.</p> 1186<h4><code>performanceResourceTiming.redirectStart</code><span><a class="mark" href="#performanceresourcetimingredirectstart" id="performanceresourcetimingredirectstart">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceresourcetiming_redirectstart"></a></h4> 1187<div class="api_metadata"> 1188<span>Added in: v18.2.0</span> 1189</div> 1190<ul> 1191<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1192</ul> 1193<p>The high resolution millisecond timestamp that represents the start time 1194of the fetch which initiates the redirect.</p> 1195<h4><code>performanceResourceTiming.redirectEnd</code><span><a class="mark" href="#performanceresourcetimingredirectend" id="performanceresourcetimingredirectend">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceresourcetiming_redirectend"></a></h4> 1196<div class="api_metadata"> 1197<span>Added in: v18.2.0</span> 1198</div> 1199<ul> 1200<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1201</ul> 1202<p>The high resolution millisecond timestamp that will be created immediately after 1203receiving the last byte of the response of the last redirect.</p> 1204<h4><code>performanceResourceTiming.fetchStart</code><span><a class="mark" href="#performanceresourcetimingfetchstart" id="performanceresourcetimingfetchstart">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceresourcetiming_fetchstart"></a></h4> 1205<div class="api_metadata"> 1206<span>Added in: v18.2.0</span> 1207</div> 1208<ul> 1209<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1210</ul> 1211<p>The high resolution millisecond timestamp immediately before the Node.js starts 1212to fetch the resource.</p> 1213<h4><code>performanceResourceTiming.domainLookupStart</code><span><a class="mark" href="#performanceresourcetimingdomainlookupstart" id="performanceresourcetimingdomainlookupstart">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceresourcetiming_domainlookupstart"></a></h4> 1214<div class="api_metadata"> 1215<span>Added in: v18.2.0</span> 1216</div> 1217<ul> 1218<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1219</ul> 1220<p>The high resolution millisecond timestamp immediately before the Node.js starts 1221the domain name lookup for the resource.</p> 1222<h4><code>performanceResourceTiming.domainLookupEnd</code><span><a class="mark" href="#performanceresourcetimingdomainlookupend" id="performanceresourcetimingdomainlookupend">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceresourcetiming_domainlookupend"></a></h4> 1223<div class="api_metadata"> 1224<span>Added in: v18.2.0</span> 1225</div> 1226<ul> 1227<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1228</ul> 1229<p>The high resolution millisecond timestamp representing the time immediately 1230after the Node.js finished the domain name lookup for the resource.</p> 1231<h4><code>performanceResourceTiming.connectStart</code><span><a class="mark" href="#performanceresourcetimingconnectstart" id="performanceresourcetimingconnectstart">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceresourcetiming_connectstart"></a></h4> 1232<div class="api_metadata"> 1233<span>Added in: v18.2.0</span> 1234</div> 1235<ul> 1236<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1237</ul> 1238<p>The high resolution millisecond timestamp representing the time immediately 1239before Node.js starts to establish the connection to the server to retrieve 1240the resource.</p> 1241<h4><code>performanceResourceTiming.connectEnd</code><span><a class="mark" href="#performanceresourcetimingconnectend" id="performanceresourcetimingconnectend">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceresourcetiming_connectend"></a></h4> 1242<div class="api_metadata"> 1243<span>Added in: v18.2.0</span> 1244</div> 1245<ul> 1246<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1247</ul> 1248<p>The high resolution millisecond timestamp representing the time immediately 1249after Node.js finishes establishing the connection to the server to retrieve 1250the resource.</p> 1251<h4><code>performanceResourceTiming.secureConnectionStart</code><span><a class="mark" href="#performanceresourcetimingsecureconnectionstart" id="performanceresourcetimingsecureconnectionstart">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceresourcetiming_secureconnectionstart"></a></h4> 1252<div class="api_metadata"> 1253<span>Added in: v18.2.0</span> 1254</div> 1255<ul> 1256<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1257</ul> 1258<p>The high resolution millisecond timestamp representing the time immediately 1259before Node.js starts the handshake process to secure the current connection.</p> 1260<h4><code>performanceResourceTiming.requestStart</code><span><a class="mark" href="#performanceresourcetimingrequeststart" id="performanceresourcetimingrequeststart">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceresourcetiming_requeststart"></a></h4> 1261<div class="api_metadata"> 1262<span>Added in: v18.2.0</span> 1263</div> 1264<ul> 1265<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1266</ul> 1267<p>The high resolution millisecond timestamp representing the time immediately 1268before Node.js receives the first byte of the response from the server.</p> 1269<h4><code>performanceResourceTiming.responseEnd</code><span><a class="mark" href="#performanceresourcetimingresponseend" id="performanceresourcetimingresponseend">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceresourcetiming_responseend"></a></h4> 1270<div class="api_metadata"> 1271<span>Added in: v18.2.0</span> 1272</div> 1273<ul> 1274<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1275</ul> 1276<p>The high resolution millisecond timestamp representing the time immediately 1277after Node.js receives the last byte of the resource or immediately before 1278the transport connection is closed, whichever comes first.</p> 1279<h4><code>performanceResourceTiming.transferSize</code><span><a class="mark" href="#performanceresourcetimingtransfersize" id="performanceresourcetimingtransfersize">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceresourcetiming_transfersize"></a></h4> 1280<div class="api_metadata"> 1281<span>Added in: v18.2.0</span> 1282</div> 1283<ul> 1284<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1285</ul> 1286<p>A number representing the size (in octets) of the fetched resource. The size 1287includes the response header fields plus the response payload body.</p> 1288<h4><code>performanceResourceTiming.encodedBodySize</code><span><a class="mark" href="#performanceresourcetimingencodedbodysize" id="performanceresourcetimingencodedbodysize">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceresourcetiming_encodedbodysize"></a></h4> 1289<div class="api_metadata"> 1290<span>Added in: v18.2.0</span> 1291</div> 1292<ul> 1293<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1294</ul> 1295<p>A number representing the size (in octets) received from the fetch 1296(HTTP or cache), of the payload body, before removing any applied 1297content-codings.</p> 1298<h4><code>performanceResourceTiming.decodedBodySize</code><span><a class="mark" href="#performanceresourcetimingdecodedbodysize" id="performanceresourcetimingdecodedbodysize">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceresourcetiming_decodedbodysize"></a></h4> 1299<div class="api_metadata"> 1300<span>Added in: v18.2.0</span> 1301</div> 1302<ul> 1303<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1304</ul> 1305<p>A number representing the size (in octets) received from the fetch 1306(HTTP or cache), of the message body, after removing any applied 1307content-codings.</p> 1308<h4><code>performanceResourceTiming.toJSON()</code><span><a class="mark" href="#performanceresourcetimingtojson" id="performanceresourcetimingtojson">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceresourcetiming_tojson"></a></h4> 1309<div class="api_metadata"> 1310<span>Added in: v18.2.0</span> 1311</div> 1312<p>Returns a <code>object</code> that is the JSON representation of the 1313<code>PerformanceResourceTiming</code> object</p> 1314</section><section><h3>Class: <code>perf_hooks.PerformanceObserver</code><span><a class="mark" href="#class-perf_hooksperformanceobserver" id="class-perf_hooksperformanceobserver">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_class_perf_hooks_performanceobserver"></a></h3> 1315<div class="api_metadata"> 1316<span>Added in: v8.5.0</span> 1317</div> 1318<h4><code>PerformanceObserver.supportedEntryTypes</code><span><a class="mark" href="#performanceobserversupportedentrytypes" id="performanceobserversupportedentrytypes">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceobserver_supportedentrytypes"></a></h4> 1319<div class="api_metadata"> 1320<span>Added in: v16.0.0</span> 1321</div> 1322<ul> 1323<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a></li> 1324</ul> 1325<p>Get supported types.</p> 1326<h4><code>new PerformanceObserver(callback)</code><span><a class="mark" href="#new-performanceobservercallback" id="new-performanceobservercallback">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_new_performanceobserver_callback"></a></h4> 1327<div class="api_metadata"> 1328<details class="changelog"><summary>History</summary> 1329<table> 1330<tbody><tr><th>Version</th><th>Changes</th></tr> 1331<tr><td>v18.0.0</td> 1332<td><p>Passing an invalid callback to the <code>callback</code> argument now throws <code>ERR_INVALID_ARG_TYPE</code> instead of <code>ERR_INVALID_CALLBACK</code>.</p></td></tr> 1333<tr><td>v8.5.0</td> 1334<td><p><span>Added in: v8.5.0</span></p></td></tr> 1335</tbody></table> 1336</details> 1337</div> 1338<ul> 1339<li><code>callback</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> 1340<ul> 1341<li><code>list</code> <a href="perf_hooks.html#class-performanceobserverentrylist" class="type"><PerformanceObserverEntryList></a></li> 1342<li><code>observer</code> <a href="perf_hooks.html#class-perf_hooksperformanceobserver" class="type"><PerformanceObserver></a></li> 1343</ul> 1344</li> 1345</ul> 1346<p><code>PerformanceObserver</code> objects provide notifications when new 1347<code>PerformanceEntry</code> instances have been added to the Performance Timeline.</p> 1348<pre><code class="language-js"><span class="hljs-keyword">const</span> { 1349 performance, 1350 <span class="hljs-title class_">PerformanceObserver</span>, 1351} = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:perf_hooks'</span>); 1352 1353<span class="hljs-keyword">const</span> obs = <span class="hljs-keyword">new</span> <span class="hljs-title class_">PerformanceObserver</span>(<span class="hljs-function">(<span class="hljs-params">list, observer</span>) =></span> { 1354 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(list.<span class="hljs-title function_">getEntries</span>()); 1355 1356 performance.<span class="hljs-title function_">clearMarks</span>(); 1357 performance.<span class="hljs-title function_">clearMeasures</span>(); 1358 observer.<span class="hljs-title function_">disconnect</span>(); 1359}); 1360obs.<span class="hljs-title function_">observe</span>({ <span class="hljs-attr">entryTypes</span>: [<span class="hljs-string">'mark'</span>], <span class="hljs-attr">buffered</span>: <span class="hljs-literal">true</span> }); 1361 1362performance.<span class="hljs-title function_">mark</span>(<span class="hljs-string">'test'</span>);</code> <button class="copy-button">copy</button></pre> 1363<p>Because <code>PerformanceObserver</code> instances introduce their own additional 1364performance overhead, instances should not be left subscribed to notifications 1365indefinitely. Users should disconnect observers as soon as they are no 1366longer needed.</p> 1367<p>The <code>callback</code> is invoked when a <code>PerformanceObserver</code> is 1368notified about new <code>PerformanceEntry</code> instances. The callback receives a 1369<code>PerformanceObserverEntryList</code> instance and a reference to the 1370<code>PerformanceObserver</code>.</p> 1371<h4><code>performanceObserver.disconnect()</code><span><a class="mark" href="#performanceobserverdisconnect" id="performanceobserverdisconnect">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceobserver_disconnect"></a></h4> 1372<div class="api_metadata"> 1373<span>Added in: v8.5.0</span> 1374</div> 1375<p>Disconnects the <code>PerformanceObserver</code> instance from all notifications.</p> 1376<h4><code>performanceObserver.observe(options)</code><span><a class="mark" href="#performanceobserverobserveoptions" id="performanceobserverobserveoptions">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceobserver_observe_options"></a></h4> 1377<div class="api_metadata"> 1378<details class="changelog"><summary>History</summary> 1379<table> 1380<tbody><tr><th>Version</th><th>Changes</th></tr> 1381<tr><td>v16.7.0</td> 1382<td><p>Updated to conform to Performance Timeline Level 2. The buffered option has been added back.</p></td></tr> 1383<tr><td>v16.0.0</td> 1384<td><p>Updated to conform to User Timing Level 3. The buffered option has been removed.</p></td></tr> 1385<tr><td>v8.5.0</td> 1386<td><p><span>Added in: v8.5.0</span></p></td></tr> 1387</tbody></table> 1388</details> 1389</div> 1390<ul> 1391<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1392<ul> 1393<li><code>type</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A single <a href="perf_hooks.html#class-performanceentry" class="type"><PerformanceEntry></a> type. Must not be given 1394if <code>entryTypes</code> is already specified.</li> 1395<li><code>entryTypes</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string[]></a> An array of strings identifying the types of 1396<a href="perf_hooks.html#class-performanceentry" class="type"><PerformanceEntry></a> instances the observer is interested in. If not 1397provided an error will be thrown.</li> 1398<li><code>buffered</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> If true, the observer callback is called with a 1399list global <code>PerformanceEntry</code> buffered entries. If false, only 1400<code>PerformanceEntry</code>s created after the time point are sent to the 1401observer callback. <strong>Default:</strong> <code>false</code>.</li> 1402</ul> 1403</li> 1404</ul> 1405<p>Subscribes the <a href="perf_hooks.html#class-perf_hooksperformanceobserver" class="type"><PerformanceObserver></a> instance to notifications of new 1406<a href="perf_hooks.html#class-performanceentry" class="type"><PerformanceEntry></a> instances identified either by <code>options.entryTypes</code> 1407or <code>options.type</code>:</p> 1408<pre><code class="language-js"><span class="hljs-keyword">const</span> { 1409 performance, 1410 <span class="hljs-title class_">PerformanceObserver</span>, 1411} = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:perf_hooks'</span>); 1412 1413<span class="hljs-keyword">const</span> obs = <span class="hljs-keyword">new</span> <span class="hljs-title class_">PerformanceObserver</span>(<span class="hljs-function">(<span class="hljs-params">list, observer</span>) =></span> { 1414 <span class="hljs-comment">// Called once asynchronously. `list` contains three items.</span> 1415}); 1416obs.<span class="hljs-title function_">observe</span>({ <span class="hljs-attr">type</span>: <span class="hljs-string">'mark'</span> }); 1417 1418<span class="hljs-keyword">for</span> (<span class="hljs-keyword">let</span> n = <span class="hljs-number">0</span>; n < <span class="hljs-number">3</span>; n++) 1419 performance.<span class="hljs-title function_">mark</span>(<span class="hljs-string">`test<span class="hljs-subst">${n}</span>`</span>);</code> <button class="copy-button">copy</button></pre> 1420</section><section><h3>Class: <code>PerformanceObserverEntryList</code><span><a class="mark" href="#class-performanceobserverentrylist" id="class-performanceobserverentrylist">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_class_performanceobserverentrylist"></a></h3> 1421<div class="api_metadata"> 1422<span>Added in: v8.5.0</span> 1423</div> 1424<p>The <code>PerformanceObserverEntryList</code> class is used to provide access to the 1425<code>PerformanceEntry</code> instances passed to a <code>PerformanceObserver</code>. 1426The constructor of this class is not exposed to users.</p> 1427<h4><code>performanceObserverEntryList.getEntries()</code><span><a class="mark" href="#performanceobserverentrylistgetentries" id="performanceobserverentrylistgetentries">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceobserverentrylist_getentries"></a></h4> 1428<div class="api_metadata"> 1429<span>Added in: v8.5.0</span> 1430</div> 1431<ul> 1432<li>Returns: <a href="perf_hooks.html#class-performanceentry" class="type"><PerformanceEntry[]></a></li> 1433</ul> 1434<p>Returns a list of <code>PerformanceEntry</code> objects in chronological order 1435with respect to <code>performanceEntry.startTime</code>.</p> 1436<pre><code class="language-js"><span class="hljs-keyword">const</span> { 1437 performance, 1438 <span class="hljs-title class_">PerformanceObserver</span>, 1439} = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:perf_hooks'</span>); 1440 1441<span class="hljs-keyword">const</span> obs = <span class="hljs-keyword">new</span> <span class="hljs-title class_">PerformanceObserver</span>(<span class="hljs-function">(<span class="hljs-params">perfObserverList, observer</span>) =></span> { 1442 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(perfObserverList.<span class="hljs-title function_">getEntries</span>()); 1443 <span class="hljs-comment">/** 1444 * [ 1445 * PerformanceEntry { 1446 * name: 'test', 1447 * entryType: 'mark', 1448 * startTime: 81.465639, 1449 * duration: 0 1450 * }, 1451 * PerformanceEntry { 1452 * name: 'meow', 1453 * entryType: 'mark', 1454 * startTime: 81.860064, 1455 * duration: 0 1456 * } 1457 * ] 1458 */</span> 1459 1460 performance.<span class="hljs-title function_">clearMarks</span>(); 1461 performance.<span class="hljs-title function_">clearMeasures</span>(); 1462 observer.<span class="hljs-title function_">disconnect</span>(); 1463}); 1464obs.<span class="hljs-title function_">observe</span>({ <span class="hljs-attr">type</span>: <span class="hljs-string">'mark'</span> }); 1465 1466performance.<span class="hljs-title function_">mark</span>(<span class="hljs-string">'test'</span>); 1467performance.<span class="hljs-title function_">mark</span>(<span class="hljs-string">'meow'</span>);</code> <button class="copy-button">copy</button></pre> 1468<h4><code>performanceObserverEntryList.getEntriesByName(name[, type])</code><span><a class="mark" href="#performanceobserverentrylistgetentriesbynamename-type" id="performanceobserverentrylistgetentriesbynamename-type">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceobserverentrylist_getentriesbyname_name_type"></a></h4> 1469<div class="api_metadata"> 1470<span>Added in: v8.5.0</span> 1471</div> 1472<ul> 1473<li><code>name</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1474<li><code>type</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1475<li>Returns: <a href="perf_hooks.html#class-performanceentry" class="type"><PerformanceEntry[]></a></li> 1476</ul> 1477<p>Returns a list of <code>PerformanceEntry</code> objects in chronological order 1478with respect to <code>performanceEntry.startTime</code> whose <code>performanceEntry.name</code> is 1479equal to <code>name</code>, and optionally, whose <code>performanceEntry.entryType</code> is equal to 1480<code>type</code>.</p> 1481<pre><code class="language-js"><span class="hljs-keyword">const</span> { 1482 performance, 1483 <span class="hljs-title class_">PerformanceObserver</span>, 1484} = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:perf_hooks'</span>); 1485 1486<span class="hljs-keyword">const</span> obs = <span class="hljs-keyword">new</span> <span class="hljs-title class_">PerformanceObserver</span>(<span class="hljs-function">(<span class="hljs-params">perfObserverList, observer</span>) =></span> { 1487 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(perfObserverList.<span class="hljs-title function_">getEntriesByName</span>(<span class="hljs-string">'meow'</span>)); 1488 <span class="hljs-comment">/** 1489 * [ 1490 * PerformanceEntry { 1491 * name: 'meow', 1492 * entryType: 'mark', 1493 * startTime: 98.545991, 1494 * duration: 0 1495 * } 1496 * ] 1497 */</span> 1498 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(perfObserverList.<span class="hljs-title function_">getEntriesByName</span>(<span class="hljs-string">'nope'</span>)); <span class="hljs-comment">// []</span> 1499 1500 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(perfObserverList.<span class="hljs-title function_">getEntriesByName</span>(<span class="hljs-string">'test'</span>, <span class="hljs-string">'mark'</span>)); 1501 <span class="hljs-comment">/** 1502 * [ 1503 * PerformanceEntry { 1504 * name: 'test', 1505 * entryType: 'mark', 1506 * startTime: 63.518931, 1507 * duration: 0 1508 * } 1509 * ] 1510 */</span> 1511 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(perfObserverList.<span class="hljs-title function_">getEntriesByName</span>(<span class="hljs-string">'test'</span>, <span class="hljs-string">'measure'</span>)); <span class="hljs-comment">// []</span> 1512 1513 performance.<span class="hljs-title function_">clearMarks</span>(); 1514 performance.<span class="hljs-title function_">clearMeasures</span>(); 1515 observer.<span class="hljs-title function_">disconnect</span>(); 1516}); 1517obs.<span class="hljs-title function_">observe</span>({ <span class="hljs-attr">entryTypes</span>: [<span class="hljs-string">'mark'</span>, <span class="hljs-string">'measure'</span>] }); 1518 1519performance.<span class="hljs-title function_">mark</span>(<span class="hljs-string">'test'</span>); 1520performance.<span class="hljs-title function_">mark</span>(<span class="hljs-string">'meow'</span>);</code> <button class="copy-button">copy</button></pre> 1521<h4><code>performanceObserverEntryList.getEntriesByType(type)</code><span><a class="mark" href="#performanceobserverentrylistgetentriesbytypetype" id="performanceobserverentrylistgetentriesbytypetype">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_performanceobserverentrylist_getentriesbytype_type"></a></h4> 1522<div class="api_metadata"> 1523<span>Added in: v8.5.0</span> 1524</div> 1525<ul> 1526<li><code>type</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> 1527<li>Returns: <a href="perf_hooks.html#class-performanceentry" class="type"><PerformanceEntry[]></a></li> 1528</ul> 1529<p>Returns a list of <code>PerformanceEntry</code> objects in chronological order 1530with respect to <code>performanceEntry.startTime</code> whose <code>performanceEntry.entryType</code> 1531is equal to <code>type</code>.</p> 1532<pre><code class="language-js"><span class="hljs-keyword">const</span> { 1533 performance, 1534 <span class="hljs-title class_">PerformanceObserver</span>, 1535} = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:perf_hooks'</span>); 1536 1537<span class="hljs-keyword">const</span> obs = <span class="hljs-keyword">new</span> <span class="hljs-title class_">PerformanceObserver</span>(<span class="hljs-function">(<span class="hljs-params">perfObserverList, observer</span>) =></span> { 1538 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(perfObserverList.<span class="hljs-title function_">getEntriesByType</span>(<span class="hljs-string">'mark'</span>)); 1539 <span class="hljs-comment">/** 1540 * [ 1541 * PerformanceEntry { 1542 * name: 'test', 1543 * entryType: 'mark', 1544 * startTime: 55.897834, 1545 * duration: 0 1546 * }, 1547 * PerformanceEntry { 1548 * name: 'meow', 1549 * entryType: 'mark', 1550 * startTime: 56.350146, 1551 * duration: 0 1552 * } 1553 * ] 1554 */</span> 1555 performance.<span class="hljs-title function_">clearMarks</span>(); 1556 performance.<span class="hljs-title function_">clearMeasures</span>(); 1557 observer.<span class="hljs-title function_">disconnect</span>(); 1558}); 1559obs.<span class="hljs-title function_">observe</span>({ <span class="hljs-attr">type</span>: <span class="hljs-string">'mark'</span> }); 1560 1561performance.<span class="hljs-title function_">mark</span>(<span class="hljs-string">'test'</span>); 1562performance.<span class="hljs-title function_">mark</span>(<span class="hljs-string">'meow'</span>);</code> <button class="copy-button">copy</button></pre> 1563</section><section><h3><code>perf_hooks.createHistogram([options])</code><span><a class="mark" href="#perf_hookscreatehistogramoptions" id="perf_hookscreatehistogramoptions">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_perf_hooks_createhistogram_options"></a></h3> 1564<div class="api_metadata"> 1565<span>Added in: v15.9.0, v14.18.0</span> 1566</div> 1567<ul> 1568<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1569<ul> 1570<li><code>lowest</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt" class="type"><bigint></a> The lowest discernible value. Must be an integer 1571value greater than 0. <strong>Default:</strong> <code>1</code>.</li> 1572<li><code>highest</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt" class="type"><bigint></a> The highest recordable value. Must be an integer 1573value that is equal to or greater than two times <code>lowest</code>. 1574<strong>Default:</strong> <code>Number.MAX_SAFE_INTEGER</code>.</li> 1575<li><code>figures</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The number of accuracy digits. Must be a number between 1576<code>1</code> and <code>5</code>. <strong>Default:</strong> <code>3</code>.</li> 1577</ul> 1578</li> 1579<li>Returns <a href="perf_hooks.html#class-recordablehistogram-extends-histogram" class="type"><RecordableHistogram></a></li> 1580</ul> 1581<p>Returns a <a href="perf_hooks.html#class-recordablehistogram-extends-histogram" class="type"><RecordableHistogram></a>.</p> 1582</section><section><h3><code>perf_hooks.monitorEventLoopDelay([options])</code><span><a class="mark" href="#perf_hooksmonitoreventloopdelayoptions" id="perf_hooksmonitoreventloopdelayoptions">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_perf_hooks_monitoreventloopdelay_options"></a></h3> 1583<div class="api_metadata"> 1584<span>Added in: v11.10.0</span> 1585</div> 1586<ul> 1587<li><code>options</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> 1588<ul> 1589<li><code>resolution</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> The sampling rate in milliseconds. Must be greater 1590than zero. <strong>Default:</strong> <code>10</code>.</li> 1591</ul> 1592</li> 1593<li>Returns: <a href="perf_hooks.html#class-intervalhistogram-extends-histogram" class="type"><IntervalHistogram></a></li> 1594</ul> 1595<p><em>This property is an extension by Node.js. It is not available in Web browsers.</em></p> 1596<p>Creates an <code>IntervalHistogram</code> object that samples and reports the event loop 1597delay over time. The delays will be reported in nanoseconds.</p> 1598<p>Using a timer to detect approximate event loop delay works because the 1599execution of timers is tied specifically to the lifecycle of the libuv 1600event loop. That is, a delay in the loop will cause a delay in the execution 1601of the timer, and those delays are specifically what this API is intended to 1602detect.</p> 1603<pre><code class="language-js"><span class="hljs-keyword">const</span> { monitorEventLoopDelay } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:perf_hooks'</span>); 1604<span class="hljs-keyword">const</span> h = <span class="hljs-title function_">monitorEventLoopDelay</span>({ <span class="hljs-attr">resolution</span>: <span class="hljs-number">20</span> }); 1605h.<span class="hljs-title function_">enable</span>(); 1606<span class="hljs-comment">// Do something.</span> 1607h.<span class="hljs-title function_">disable</span>(); 1608<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(h.<span class="hljs-property">min</span>); 1609<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(h.<span class="hljs-property">max</span>); 1610<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(h.<span class="hljs-property">mean</span>); 1611<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(h.<span class="hljs-property">stddev</span>); 1612<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(h.<span class="hljs-property">percentiles</span>); 1613<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(h.<span class="hljs-title function_">percentile</span>(<span class="hljs-number">50</span>)); 1614<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(h.<span class="hljs-title function_">percentile</span>(<span class="hljs-number">99</span>));</code> <button class="copy-button">copy</button></pre> 1615</section><section><h3>Class: <code>Histogram</code><span><a class="mark" href="#class-histogram" id="class-histogram">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_class_histogram"></a></h3> 1616<div class="api_metadata"> 1617<span>Added in: v11.10.0</span> 1618</div> 1619<h4><code>histogram.count</code><span><a class="mark" href="#histogramcount" id="histogramcount">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_histogram_count"></a></h4> 1620<div class="api_metadata"> 1621<span>Added in: v17.4.0, v16.14.0</span> 1622</div> 1623<ul> 1624<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1625</ul> 1626<p>The number of samples recorded by the histogram.</p> 1627<h4><code>histogram.countBigInt</code><span><a class="mark" href="#histogramcountbigint" id="histogramcountbigint">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_histogram_countbigint"></a></h4> 1628<div class="api_metadata"> 1629<span>Added in: v17.4.0, v16.14.0</span> 1630</div> 1631<ul> 1632<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt" class="type"><bigint></a></li> 1633</ul> 1634<p>The number of samples recorded by the histogram.</p> 1635<h4><code>histogram.exceeds</code><span><a class="mark" href="#histogramexceeds" id="histogramexceeds">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_histogram_exceeds"></a></h4> 1636<div class="api_metadata"> 1637<span>Added in: v11.10.0</span> 1638</div> 1639<ul> 1640<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1641</ul> 1642<p>The number of times the event loop delay exceeded the maximum 1 hour event 1643loop delay threshold.</p> 1644<h4><code>histogram.exceedsBigInt</code><span><a class="mark" href="#histogramexceedsbigint" id="histogramexceedsbigint">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_histogram_exceedsbigint"></a></h4> 1645<div class="api_metadata"> 1646<span>Added in: v17.4.0, v16.14.0</span> 1647</div> 1648<ul> 1649<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt" class="type"><bigint></a></li> 1650</ul> 1651<p>The number of times the event loop delay exceeded the maximum 1 hour event 1652loop delay threshold.</p> 1653<h4><code>histogram.max</code><span><a class="mark" href="#histogrammax" id="histogrammax">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_histogram_max"></a></h4> 1654<div class="api_metadata"> 1655<span>Added in: v11.10.0</span> 1656</div> 1657<ul> 1658<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1659</ul> 1660<p>The maximum recorded event loop delay.</p> 1661<h4><code>histogram.maxBigInt</code><span><a class="mark" href="#histogrammaxbigint" id="histogrammaxbigint">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_histogram_maxbigint"></a></h4> 1662<div class="api_metadata"> 1663<span>Added in: v17.4.0, v16.14.0</span> 1664</div> 1665<ul> 1666<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt" class="type"><bigint></a></li> 1667</ul> 1668<p>The maximum recorded event loop delay.</p> 1669<h4><code>histogram.mean</code><span><a class="mark" href="#histogrammean" id="histogrammean">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_histogram_mean"></a></h4> 1670<div class="api_metadata"> 1671<span>Added in: v11.10.0</span> 1672</div> 1673<ul> 1674<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1675</ul> 1676<p>The mean of the recorded event loop delays.</p> 1677<h4><code>histogram.min</code><span><a class="mark" href="#histogrammin" id="histogrammin">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_histogram_min"></a></h4> 1678<div class="api_metadata"> 1679<span>Added in: v11.10.0</span> 1680</div> 1681<ul> 1682<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1683</ul> 1684<p>The minimum recorded event loop delay.</p> 1685<h4><code>histogram.minBigInt</code><span><a class="mark" href="#histogramminbigint" id="histogramminbigint">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_histogram_minbigint"></a></h4> 1686<div class="api_metadata"> 1687<span>Added in: v17.4.0, v16.14.0</span> 1688</div> 1689<ul> 1690<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt" class="type"><bigint></a></li> 1691</ul> 1692<p>The minimum recorded event loop delay.</p> 1693<h4><code>histogram.percentile(percentile)</code><span><a class="mark" href="#histogrampercentilepercentile" id="histogrampercentilepercentile">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_histogram_percentile_percentile"></a></h4> 1694<div class="api_metadata"> 1695<span>Added in: v11.10.0</span> 1696</div> 1697<ul> 1698<li><code>percentile</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> A percentile value in the range (0, 100].</li> 1699<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1700</ul> 1701<p>Returns the value at the given percentile.</p> 1702<h4><code>histogram.percentileBigInt(percentile)</code><span><a class="mark" href="#histogrampercentilebigintpercentile" id="histogrampercentilebigintpercentile">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_histogram_percentilebigint_percentile"></a></h4> 1703<div class="api_metadata"> 1704<span>Added in: v17.4.0, v16.14.0</span> 1705</div> 1706<ul> 1707<li><code>percentile</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> A percentile value in the range (0, 100].</li> 1708<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt" class="type"><bigint></a></li> 1709</ul> 1710<p>Returns the value at the given percentile.</p> 1711<h4><code>histogram.percentiles</code><span><a class="mark" href="#histogrampercentiles" id="histogrampercentiles">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_histogram_percentiles"></a></h4> 1712<div class="api_metadata"> 1713<span>Added in: v11.10.0</span> 1714</div> 1715<ul> 1716<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map" class="type"><Map></a></li> 1717</ul> 1718<p>Returns a <code>Map</code> object detailing the accumulated percentile distribution.</p> 1719<h4><code>histogram.percentilesBigInt</code><span><a class="mark" href="#histogrampercentilesbigint" id="histogrampercentilesbigint">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_histogram_percentilesbigint"></a></h4> 1720<div class="api_metadata"> 1721<span>Added in: v17.4.0, v16.14.0</span> 1722</div> 1723<ul> 1724<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map" class="type"><Map></a></li> 1725</ul> 1726<p>Returns a <code>Map</code> object detailing the accumulated percentile distribution.</p> 1727<h4><code>histogram.reset()</code><span><a class="mark" href="#histogramreset" id="histogramreset">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_histogram_reset"></a></h4> 1728<div class="api_metadata"> 1729<span>Added in: v11.10.0</span> 1730</div> 1731<p>Resets the collected histogram data.</p> 1732<h4><code>histogram.stddev</code><span><a class="mark" href="#histogramstddev" id="histogramstddev">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_histogram_stddev"></a></h4> 1733<div class="api_metadata"> 1734<span>Added in: v11.10.0</span> 1735</div> 1736<ul> 1737<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> 1738</ul> 1739<p>The standard deviation of the recorded event loop delays.</p> 1740</section><section><h3>Class: <code>IntervalHistogram extends Histogram</code><span><a class="mark" href="#class-intervalhistogram-extends-histogram" id="class-intervalhistogram-extends-histogram">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_class_intervalhistogram_extends_histogram"></a></h3> 1741<p>A <code>Histogram</code> that is periodically updated on a given interval.</p> 1742<h4><code>histogram.disable()</code><span><a class="mark" href="#histogramdisable" id="histogramdisable">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_histogram_disable"></a></h4> 1743<div class="api_metadata"> 1744<span>Added in: v11.10.0</span> 1745</div> 1746<ul> 1747<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1748</ul> 1749<p>Disables the update interval timer. Returns <code>true</code> if the timer was 1750stopped, <code>false</code> if it was already stopped.</p> 1751<h4><code>histogram.enable()</code><span><a class="mark" href="#histogramenable" id="histogramenable">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_histogram_enable"></a></h4> 1752<div class="api_metadata"> 1753<span>Added in: v11.10.0</span> 1754</div> 1755<ul> 1756<li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> 1757</ul> 1758<p>Enables the update interval timer. Returns <code>true</code> if the timer was 1759started, <code>false</code> if it was already started.</p> 1760<h4>Cloning an <code>IntervalHistogram</code><span><a class="mark" href="#cloning-an-intervalhistogram" id="cloning-an-intervalhistogram">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_cloning_an_intervalhistogram"></a></h4> 1761<p><a href="perf_hooks.html#class-intervalhistogram-extends-histogram" class="type"><IntervalHistogram></a> instances can be cloned via <a href="worker_threads.html#class-messageport" class="type"><MessagePort></a>. On the receiving 1762end, the histogram is cloned as a plain <a href="perf_hooks.html#class-histogram" class="type"><Histogram></a> object that does not 1763implement the <code>enable()</code> and <code>disable()</code> methods.</p> 1764</section><section><h3>Class: <code>RecordableHistogram extends Histogram</code><span><a class="mark" href="#class-recordablehistogram-extends-histogram" id="class-recordablehistogram-extends-histogram">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_class_recordablehistogram_extends_histogram"></a></h3> 1765<div class="api_metadata"> 1766<span>Added in: v15.9.0, v14.18.0</span> 1767</div> 1768<h4><code>histogram.add(other)</code><span><a class="mark" href="#histogramaddother" id="histogramaddother">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_histogram_add_other"></a></h4> 1769<div class="api_metadata"> 1770<span>Added in: v17.4.0, v16.14.0</span> 1771</div> 1772<ul> 1773<li><code>other</code> <a href="perf_hooks.html#class-recordablehistogram-extends-histogram" class="type"><RecordableHistogram></a></li> 1774</ul> 1775<p>Adds the values from <code>other</code> to this histogram.</p> 1776<h4><code>histogram.record(val)</code><span><a class="mark" href="#histogramrecordval" id="histogramrecordval">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_histogram_record_val"></a></h4> 1777<div class="api_metadata"> 1778<span>Added in: v15.9.0, v14.18.0</span> 1779</div> 1780<ul> 1781<li><code>val</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt" class="type"><bigint></a> The amount to record in the histogram.</li> 1782</ul> 1783<h4><code>histogram.recordDelta()</code><span><a class="mark" href="#histogramrecorddelta" id="histogramrecorddelta">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_histogram_recorddelta"></a></h4> 1784<div class="api_metadata"> 1785<span>Added in: v15.9.0, v14.18.0</span> 1786</div> 1787<p>Calculates the amount of time (in nanoseconds) that has passed since the 1788previous call to <code>recordDelta()</code> and records that amount in the histogram.</p> 1789</section><section><h3>Examples<span><a class="mark" href="#examples" id="examples">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_examples"></a></h3> 1790<h4>Measuring the duration of async operations<span><a class="mark" href="#measuring-the-duration-of-async-operations" id="measuring-the-duration-of-async-operations">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_measuring_the_duration_of_async_operations"></a></h4> 1791<p>The following example uses the <a href="async_hooks.html">Async Hooks</a> and Performance APIs to measure 1792the actual duration of a Timeout operation (including the amount of time it took 1793to execute the callback).</p> 1794<pre><code class="language-js"><span class="hljs-meta">'use strict'</span>; 1795<span class="hljs-keyword">const</span> async_hooks = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:async_hooks'</span>); 1796<span class="hljs-keyword">const</span> { 1797 performance, 1798 <span class="hljs-title class_">PerformanceObserver</span>, 1799} = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:perf_hooks'</span>); 1800 1801<span class="hljs-keyword">const</span> set = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Set</span>(); 1802<span class="hljs-keyword">const</span> hook = async_hooks.<span class="hljs-title function_">createHook</span>({ 1803 <span class="hljs-title function_">init</span>(<span class="hljs-params">id, type</span>) { 1804 <span class="hljs-keyword">if</span> (type === <span class="hljs-string">'Timeout'</span>) { 1805 performance.<span class="hljs-title function_">mark</span>(<span class="hljs-string">`Timeout-<span class="hljs-subst">${id}</span>-Init`</span>); 1806 set.<span class="hljs-title function_">add</span>(id); 1807 } 1808 }, 1809 <span class="hljs-title function_">destroy</span>(<span class="hljs-params">id</span>) { 1810 <span class="hljs-keyword">if</span> (set.<span class="hljs-title function_">has</span>(id)) { 1811 set.<span class="hljs-title function_">delete</span>(id); 1812 performance.<span class="hljs-title function_">mark</span>(<span class="hljs-string">`Timeout-<span class="hljs-subst">${id}</span>-Destroy`</span>); 1813 performance.<span class="hljs-title function_">measure</span>(<span class="hljs-string">`Timeout-<span class="hljs-subst">${id}</span>`</span>, 1814 <span class="hljs-string">`Timeout-<span class="hljs-subst">${id}</span>-Init`</span>, 1815 <span class="hljs-string">`Timeout-<span class="hljs-subst">${id}</span>-Destroy`</span>); 1816 } 1817 }, 1818}); 1819hook.<span class="hljs-title function_">enable</span>(); 1820 1821<span class="hljs-keyword">const</span> obs = <span class="hljs-keyword">new</span> <span class="hljs-title class_">PerformanceObserver</span>(<span class="hljs-function">(<span class="hljs-params">list, observer</span>) =></span> { 1822 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(list.<span class="hljs-title function_">getEntries</span>()[<span class="hljs-number">0</span>]); 1823 performance.<span class="hljs-title function_">clearMarks</span>(); 1824 performance.<span class="hljs-title function_">clearMeasures</span>(); 1825 observer.<span class="hljs-title function_">disconnect</span>(); 1826}); 1827obs.<span class="hljs-title function_">observe</span>({ <span class="hljs-attr">entryTypes</span>: [<span class="hljs-string">'measure'</span>], <span class="hljs-attr">buffered</span>: <span class="hljs-literal">true</span> }); 1828 1829<span class="hljs-built_in">setTimeout</span>(<span class="hljs-function">() =></span> {}, <span class="hljs-number">1000</span>);</code> <button class="copy-button">copy</button></pre> 1830<h4>Measuring how long it takes to load dependencies<span><a class="mark" href="#measuring-how-long-it-takes-to-load-dependencies" id="measuring-how-long-it-takes-to-load-dependencies">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_measuring_how_long_it_takes_to_load_dependencies"></a></h4> 1831<p>The following example measures the duration of <code>require()</code> operations to load 1832dependencies:</p> 1833<!-- eslint-disable no-global-assign --> 1834<pre><code class="language-js"><span class="hljs-meta">'use strict'</span>; 1835<span class="hljs-keyword">const</span> { 1836 performance, 1837 <span class="hljs-title class_">PerformanceObserver</span>, 1838} = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:perf_hooks'</span>); 1839<span class="hljs-keyword">const</span> mod = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:module'</span>); 1840 1841<span class="hljs-comment">// Monkey patch the require function</span> 1842mod.<span class="hljs-property">Module</span>.<span class="hljs-property"><span class="hljs-keyword">prototype</span></span>.<span class="hljs-property">require</span> = 1843 performance.<span class="hljs-title function_">timerify</span>(mod.<span class="hljs-property">Module</span>.<span class="hljs-property"><span class="hljs-keyword">prototype</span></span>.<span class="hljs-property">require</span>); 1844<span class="hljs-built_in">require</span> = performance.<span class="hljs-title function_">timerify</span>(<span class="hljs-built_in">require</span>); 1845 1846<span class="hljs-comment">// Activate the observer</span> 1847<span class="hljs-keyword">const</span> obs = <span class="hljs-keyword">new</span> <span class="hljs-title class_">PerformanceObserver</span>(<span class="hljs-function">(<span class="hljs-params">list</span>) =></span> { 1848 <span class="hljs-keyword">const</span> entries = list.<span class="hljs-title function_">getEntries</span>(); 1849 entries.<span class="hljs-title function_">forEach</span>(<span class="hljs-function">(<span class="hljs-params">entry</span>) =></span> { 1850 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">`require('<span class="hljs-subst">${entry[<span class="hljs-number">0</span>]}</span>')`</span>, entry.<span class="hljs-property">duration</span>); 1851 }); 1852 performance.<span class="hljs-title function_">clearMarks</span>(); 1853 performance.<span class="hljs-title function_">clearMeasures</span>(); 1854 obs.<span class="hljs-title function_">disconnect</span>(); 1855}); 1856obs.<span class="hljs-title function_">observe</span>({ <span class="hljs-attr">entryTypes</span>: [<span class="hljs-string">'function'</span>], <span class="hljs-attr">buffered</span>: <span class="hljs-literal">true</span> }); 1857 1858<span class="hljs-built_in">require</span>(<span class="hljs-string">'some-module'</span>);</code> <button class="copy-button">copy</button></pre> 1859<h4>Measuring how long one HTTP round-trip takes<span><a class="mark" href="#measuring-how-long-one-http-round-trip-takes" id="measuring-how-long-one-http-round-trip-takes">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_measuring_how_long_one_http_round_trip_takes"></a></h4> 1860<p>The following example is used to trace the time spent by HTTP client 1861(<code>OutgoingMessage</code>) and HTTP request (<code>IncomingMessage</code>). For HTTP client, 1862it means the time interval between starting the request and receiving the 1863response, and for HTTP request, it means the time interval between receiving 1864the request and sending the response:</p> 1865<pre><code class="language-js"><span class="hljs-meta">'use strict'</span>; 1866<span class="hljs-keyword">const</span> { <span class="hljs-title class_">PerformanceObserver</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:perf_hooks'</span>); 1867<span class="hljs-keyword">const</span> http = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:http'</span>); 1868 1869<span class="hljs-keyword">const</span> obs = <span class="hljs-keyword">new</span> <span class="hljs-title class_">PerformanceObserver</span>(<span class="hljs-function">(<span class="hljs-params">items</span>) =></span> { 1870 items.<span class="hljs-title function_">getEntries</span>().<span class="hljs-title function_">forEach</span>(<span class="hljs-function">(<span class="hljs-params">item</span>) =></span> { 1871 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(item); 1872 }); 1873}); 1874 1875obs.<span class="hljs-title function_">observe</span>({ <span class="hljs-attr">entryTypes</span>: [<span class="hljs-string">'http'</span>] }); 1876 1877<span class="hljs-keyword">const</span> <span class="hljs-variable constant_">PORT</span> = <span class="hljs-number">8080</span>; 1878 1879http.<span class="hljs-title function_">createServer</span>(<span class="hljs-function">(<span class="hljs-params">req, res</span>) =></span> { 1880 res.<span class="hljs-title function_">end</span>(<span class="hljs-string">'ok'</span>); 1881}).<span class="hljs-title function_">listen</span>(<span class="hljs-variable constant_">PORT</span>, <span class="hljs-function">() =></span> { 1882 http.<span class="hljs-title function_">get</span>(<span class="hljs-string">`http://127.0.0.1:<span class="hljs-subst">${PORT}</span>`</span>); 1883});</code> <button class="copy-button">copy</button></pre> 1884<h4>Measuring how long the <code>net.connect</code> (only for TCP) takes when the connection is successful<span><a class="mark" href="#measuring-how-long-the-netconnect-only-for-tcp-takes-when-the-connection-is-successful" id="measuring-how-long-the-netconnect-only-for-tcp-takes-when-the-connection-is-successful">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_measuring_how_long_the_net_connect_only_for_tcp_takes_when_the_connection_is_successful"></a></h4> 1885<pre><code class="language-js"><span class="hljs-meta">'use strict'</span>; 1886<span class="hljs-keyword">const</span> { <span class="hljs-title class_">PerformanceObserver</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:perf_hooks'</span>); 1887<span class="hljs-keyword">const</span> net = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:net'</span>); 1888<span class="hljs-keyword">const</span> obs = <span class="hljs-keyword">new</span> <span class="hljs-title class_">PerformanceObserver</span>(<span class="hljs-function">(<span class="hljs-params">items</span>) =></span> { 1889 items.<span class="hljs-title function_">getEntries</span>().<span class="hljs-title function_">forEach</span>(<span class="hljs-function">(<span class="hljs-params">item</span>) =></span> { 1890 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(item); 1891 }); 1892}); 1893obs.<span class="hljs-title function_">observe</span>({ <span class="hljs-attr">entryTypes</span>: [<span class="hljs-string">'net'</span>] }); 1894<span class="hljs-keyword">const</span> <span class="hljs-variable constant_">PORT</span> = <span class="hljs-number">8080</span>; 1895net.<span class="hljs-title function_">createServer</span>(<span class="hljs-function">(<span class="hljs-params">socket</span>) =></span> { 1896 socket.<span class="hljs-title function_">destroy</span>(); 1897}).<span class="hljs-title function_">listen</span>(<span class="hljs-variable constant_">PORT</span>, <span class="hljs-function">() =></span> { 1898 net.<span class="hljs-title function_">connect</span>(<span class="hljs-variable constant_">PORT</span>); 1899});</code> <button class="copy-button">copy</button></pre> 1900<h4>Measuring how long the DNS takes when the request is successful<span><a class="mark" href="#measuring-how-long-the-dns-takes-when-the-request-is-successful" id="measuring-how-long-the-dns-takes-when-the-request-is-successful">#</a></span><a aria-hidden="true" class="legacy" id="perf_hooks_measuring_how_long_the_dns_takes_when_the_request_is_successful"></a></h4> 1901<pre><code class="language-js"><span class="hljs-meta">'use strict'</span>; 1902<span class="hljs-keyword">const</span> { <span class="hljs-title class_">PerformanceObserver</span> } = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:perf_hooks'</span>); 1903<span class="hljs-keyword">const</span> dns = <span class="hljs-built_in">require</span>(<span class="hljs-string">'node:dns'</span>); 1904<span class="hljs-keyword">const</span> obs = <span class="hljs-keyword">new</span> <span class="hljs-title class_">PerformanceObserver</span>(<span class="hljs-function">(<span class="hljs-params">items</span>) =></span> { 1905 items.<span class="hljs-title function_">getEntries</span>().<span class="hljs-title function_">forEach</span>(<span class="hljs-function">(<span class="hljs-params">item</span>) =></span> { 1906 <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(item); 1907 }); 1908}); 1909obs.<span class="hljs-title function_">observe</span>({ <span class="hljs-attr">entryTypes</span>: [<span class="hljs-string">'dns'</span>] }); 1910dns.<span class="hljs-title function_">lookup</span>(<span class="hljs-string">'localhost'</span>, <span class="hljs-function">() =></span> {}); 1911dns.<span class="hljs-property">promises</span>.<span class="hljs-title function_">resolve</span>(<span class="hljs-string">'localhost'</span>);</code> <button class="copy-button">copy</button></pre></section> 1912 <!-- API END --> 1913 </div> 1914 </div> 1915 </div> 1916</body> 1917</html> 1918