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href="https://nodejs.org/docs/latest-v20.x/api/embedding.html">20.x <b>LTS</b></a></li> 229<li><a href="https://nodejs.org/docs/latest-v19.x/api/embedding.html">19.x</a></li> 230<li><a href="https://nodejs.org/docs/latest-v18.x/api/embedding.html">18.x <b>LTS</b></a></li> 231<li><a href="https://nodejs.org/docs/latest-v17.x/api/embedding.html">17.x</a></li> 232<li><a href="https://nodejs.org/docs/latest-v16.x/api/embedding.html">16.x</a></li> 233<li><a href="https://nodejs.org/docs/latest-v15.x/api/embedding.html">15.x</a></li> 234<li><a href="https://nodejs.org/docs/latest-v14.x/api/embedding.html">14.x</a></li> 235<li><a href="https://nodejs.org/docs/latest-v13.x/api/embedding.html">13.x</a></li> 236<li><a href="https://nodejs.org/docs/latest-v12.x/api/embedding.html">12.x</a></li></ol></div> 237 </li> 238 239 <li class="picker-header"> 240 <a href="#"> 241 <span class="collapsed-arrow">►</span><span class="expanded-arrow">▼</span> 242 Options 243 </a> 244 245 <div class="picker"> 246 <ul> 247 <li> 248 <a href="all.html">View on single page</a> 249 </li> 250 <li> 251 <a href="embedding.json">View as JSON</a> 252 </li> 253 <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/main/doc/api/embedding.md">Edit on GitHub</a></li> 254 </ul> 255 </div> 256 </li> 257 </ul> 258 </div> 259 <hr> 260 </header> 261 262 <details id="toc" open><summary>Table of contents</summary><ul> 263<li><a href="#c-embedder-api">C++ embedder API</a> 264<ul> 265<li><a href="#example-embedding-application">Example embedding application</a> 266<ul> 267<li><a href="#setting-up-per-process-state">Setting up per-process state</a></li> 268<li><a href="#per-instance-state">Per-instance state</a></li> 269</ul> 270</li> 271</ul> 272</li> 273</ul></details> 274 275 <div id="apicontent"> 276 <h2>C++ embedder API<span><a class="mark" href="#c-embedder-api" id="c-embedder-api">#</a></span><a aria-hidden="true" class="legacy" id="embedding_c_embedder_api"></a></h2> 277 278<p>Node.js provides a number of C++ APIs that can be used to execute JavaScript 279in a Node.js environment from other C++ software.</p> 280<p>The documentation for these APIs can be found in <a href="https://github.com/nodejs/node/blob/HEAD/src/node.h">src/node.h</a> in the Node.js 281source tree. In addition to the APIs exposed by Node.js, some required concepts 282are provided by the V8 embedder API.</p> 283<p>Because using Node.js as an embedded library is different from writing code 284that is executed by Node.js, breaking changes do not follow typical Node.js 285<a href="deprecations.html">deprecation policy</a> and may occur on each semver-major release without prior 286warning.</p> 287<section><h3>Example embedding application<span><a class="mark" href="#example-embedding-application" id="example-embedding-application">#</a></span><a aria-hidden="true" class="legacy" id="embedding_example_embedding_application"></a></h3> 288<p>The following sections will provide an overview over how to use these APIs 289to create an application from scratch that will perform the equivalent of 290<code>node -e <code></code>, i.e. that will take a piece of JavaScript and run it in 291a Node.js-specific environment.</p> 292<p>The full code can be found <a href="https://github.com/nodejs/node/blob/HEAD/test/embedding/embedtest.cc">in the Node.js source tree</a>.</p> 293<h4>Setting up per-process state<span><a class="mark" href="#setting-up-per-process-state" id="setting-up-per-process-state">#</a></span><a aria-hidden="true" class="legacy" id="embedding_setting_up_per_process_state"></a></h4> 294<p>Node.js requires some per-process state management in order to run:</p> 295<ul> 296<li>Arguments parsing for Node.js <a href="cli.html">CLI options</a>,</li> 297<li>V8 per-process requirements, such as a <code>v8::Platform</code> instance.</li> 298</ul> 299<p>The following example shows how these can be set up. Some class names are from 300the <code>node</code> and <code>v8</code> C++ namespaces, respectively.</p> 301<pre><code class="language-cpp"><span class="hljs-function"><span class="hljs-type">int</span> <span class="hljs-title">main</span><span class="hljs-params">(<span class="hljs-type">int</span> argc, <span class="hljs-type">char</span>** argv)</span> </span>{ 302 argv = <span class="hljs-built_in">uv_setup_args</span>(argc, argv); 303 <span class="hljs-function">std::vector<std::string> <span class="hljs-title">args</span><span class="hljs-params">(argv, argv + argc)</span></span>; 304 <span class="hljs-comment">// Parse Node.js CLI options, and print any errors that have occurred while</span> 305 <span class="hljs-comment">// trying to parse them.</span> 306 std::unique_ptr<node::InitializationResult> result = 307 node::<span class="hljs-built_in">InitializeOncePerProcess</span>(args, { 308 node::ProcessInitializationFlags::kNoInitializeV8, 309 node::ProcessInitializationFlags::kNoInitializeNodeV8Platform 310 }); 311 312 <span class="hljs-keyword">for</span> (<span class="hljs-type">const</span> std::string& error : result-><span class="hljs-built_in">errors</span>()) 313 <span class="hljs-built_in">fprintf</span>(stderr, <span class="hljs-string">"%s: %s\n"</span>, args[<span class="hljs-number">0</span>].<span class="hljs-built_in">c_str</span>(), error.<span class="hljs-built_in">c_str</span>()); 314 <span class="hljs-keyword">if</span> (result-><span class="hljs-built_in">early_return</span>() != <span class="hljs-number">0</span>) { 315 <span class="hljs-keyword">return</span> result-><span class="hljs-built_in">exit_code</span>(); 316 } 317 318 <span class="hljs-comment">// Create a v8::Platform instance. `MultiIsolatePlatform::Create()` is a way</span> 319 <span class="hljs-comment">// to create a v8::Platform instance that Node.js can use when creating</span> 320 <span class="hljs-comment">// Worker threads. When no `MultiIsolatePlatform` instance is present,</span> 321 <span class="hljs-comment">// Worker threads are disabled.</span> 322 std::unique_ptr<MultiIsolatePlatform> platform = 323 MultiIsolatePlatform::<span class="hljs-built_in">Create</span>(<span class="hljs-number">4</span>); 324 V8::<span class="hljs-built_in">InitializePlatform</span>(platform.<span class="hljs-built_in">get</span>()); 325 V8::<span class="hljs-built_in">Initialize</span>(); 326 327 <span class="hljs-comment">// See below for the contents of this function.</span> 328 <span class="hljs-type">int</span> ret = <span class="hljs-built_in">RunNodeInstance</span>( 329 platform.<span class="hljs-built_in">get</span>(), result-><span class="hljs-built_in">args</span>(), result-><span class="hljs-built_in">exec_args</span>()); 330 331 V8::<span class="hljs-built_in">Dispose</span>(); 332 V8::<span class="hljs-built_in">DisposePlatform</span>(); 333 334 node::<span class="hljs-built_in">TearDownOncePerProcess</span>(); 335 <span class="hljs-keyword">return</span> ret; 336}</code> <button class="copy-button">copy</button></pre> 337<h4>Per-instance state<span><a class="mark" href="#per-instance-state" id="per-instance-state">#</a></span><a aria-hidden="true" class="legacy" id="embedding_per_instance_state"></a></h4> 338<div class="api_metadata"> 339<details class="changelog"><summary>History</summary> 340<table> 341<tbody><tr><th>Version</th><th>Changes</th></tr> 342<tr><td>v15.0.0</td> 343<td><p>The <code>CommonEnvironmentSetup</code> and <code>SpinEventLoop</code> utilities were added.</p></td></tr> 344</tbody></table> 345</details> 346</div> 347<p>Node.js has a concept of a “Node.js instance”, that is commonly being referred 348to as <code>node::Environment</code>. Each <code>node::Environment</code> is associated with:</p> 349<ul> 350<li>Exactly one <code>v8::Isolate</code>, i.e. one JS Engine instance,</li> 351<li>Exactly one <code>uv_loop_t</code>, i.e. one event loop, and</li> 352<li>A number of <code>v8::Context</code>s, but exactly one main <code>v8::Context</code>.</li> 353<li>One <code>node::IsolateData</code> instance that contains information that could be 354shared by multiple <code>node::Environment</code>s that use the same <code>v8::Isolate</code>. 355Currently, no testing if performed for this scenario.</li> 356</ul> 357<p>In order to set up a <code>v8::Isolate</code>, an <code>v8::ArrayBuffer::Allocator</code> needs 358to be provided. One possible choice is the default Node.js allocator, which 359can be created through <code>node::ArrayBufferAllocator::Create()</code>. Using the Node.js 360allocator allows minor performance optimizations when addons use the Node.js 361C++ <code>Buffer</code> API, and is required in order to track <code>ArrayBuffer</code> memory in 362<a href="process.html#processmemoryusage"><code>process.memoryUsage()</code></a>.</p> 363<p>Additionally, each <code>v8::Isolate</code> that is used for a Node.js instance needs to 364be registered and unregistered with the <code>MultiIsolatePlatform</code> instance, if one 365is being used, in order for the platform to know which event loop to use 366for tasks scheduled by the <code>v8::Isolate</code>.</p> 367<p>The <code>node::NewIsolate()</code> helper function creates a <code>v8::Isolate</code>, 368sets it up with some Node.js-specific hooks (e.g. the Node.js error handler), 369and registers it with the platform automatically.</p> 370<pre><code class="language-cpp"><span class="hljs-function"><span class="hljs-type">int</span> <span class="hljs-title">RunNodeInstance</span><span class="hljs-params">(MultiIsolatePlatform* platform, 371 <span class="hljs-type">const</span> std::vector<std::string>& args, 372 <span class="hljs-type">const</span> std::vector<std::string>& exec_args)</span> </span>{ 373 <span class="hljs-type">int</span> exit_code = <span class="hljs-number">0</span>; 374 375 <span class="hljs-comment">// Setup up a libuv event loop, v8::Isolate, and Node.js Environment.</span> 376 std::vector<std::string> errors; 377 std::unique_ptr<CommonEnvironmentSetup> setup = 378 CommonEnvironmentSetup::<span class="hljs-built_in">Create</span>(platform, &errors, args, exec_args); 379 <span class="hljs-keyword">if</span> (!setup) { 380 <span class="hljs-keyword">for</span> (<span class="hljs-type">const</span> std::string& err : errors) 381 <span class="hljs-built_in">fprintf</span>(stderr, <span class="hljs-string">"%s: %s\n"</span>, args[<span class="hljs-number">0</span>].<span class="hljs-built_in">c_str</span>(), err.<span class="hljs-built_in">c_str</span>()); 382 <span class="hljs-keyword">return</span> <span class="hljs-number">1</span>; 383 } 384 385 Isolate* isolate = setup-><span class="hljs-built_in">isolate</span>(); 386 Environment* env = setup-><span class="hljs-built_in">env</span>(); 387 388 { 389 <span class="hljs-function">Locker <span class="hljs-title">locker</span><span class="hljs-params">(isolate)</span></span>; 390 <span class="hljs-function">Isolate::Scope <span class="hljs-title">isolate_scope</span><span class="hljs-params">(isolate)</span></span>; 391 <span class="hljs-function">HandleScope <span class="hljs-title">handle_scope</span><span class="hljs-params">(isolate)</span></span>; 392 <span class="hljs-comment">// The v8::Context needs to be entered when node::CreateEnvironment() and</span> 393 <span class="hljs-comment">// node::LoadEnvironment() are being called.</span> 394 <span class="hljs-function">Context::Scope <span class="hljs-title">context_scope</span><span class="hljs-params">(setup->context())</span></span>; 395 396 <span class="hljs-comment">// Set up the Node.js instance for execution, and run code inside of it.</span> 397 <span class="hljs-comment">// There is also a variant that takes a callback and provides it with</span> 398 <span class="hljs-comment">// the `require` and `process` objects, so that it can manually compile</span> 399 <span class="hljs-comment">// and run scripts as needed.</span> 400 <span class="hljs-comment">// The `require` function inside this script does *not* access the file</span> 401 <span class="hljs-comment">// system, and can only load built-in Node.js modules.</span> 402 <span class="hljs-comment">// `module.createRequire()` is being used to create one that is able to</span> 403 <span class="hljs-comment">// load files from the disk, and uses the standard CommonJS file loader</span> 404 <span class="hljs-comment">// instead of the internal-only `require` function.</span> 405 MaybeLocal<Value> loadenv_ret = node::<span class="hljs-built_in">LoadEnvironment</span>( 406 env, 407 <span class="hljs-string">"const publicRequire ="</span> 408 <span class="hljs-string">" require('node:module').createRequire(process.cwd() + '/');"</span> 409 <span class="hljs-string">"globalThis.require = publicRequire;"</span> 410 <span class="hljs-string">"require('node:vm').runInThisContext(process.argv[1]);"</span>); 411 412 <span class="hljs-keyword">if</span> (loadenv_ret.<span class="hljs-built_in">IsEmpty</span>()) <span class="hljs-comment">// There has been a JS exception.</span> 413 <span class="hljs-keyword">return</span> <span class="hljs-number">1</span>; 414 415 exit_code = node::<span class="hljs-built_in">SpinEventLoop</span>(env).<span class="hljs-built_in">FromMaybe</span>(<span class="hljs-number">1</span>); 416 417 <span class="hljs-comment">// node::Stop() can be used to explicitly stop the event loop and keep</span> 418 <span class="hljs-comment">// further JavaScript from running. It can be called from any thread,</span> 419 <span class="hljs-comment">// and will act like worker.terminate() if called from another thread.</span> 420 node::<span class="hljs-built_in">Stop</span>(env); 421 } 422 423 <span class="hljs-keyword">return</span> exit_code; 424}</code> <button class="copy-button">copy</button></pre></section> 425 <!-- API END --> 426 </div> 427 </div> 428 </div> 429</body> 430</html> 431