1# pseudomap 2 3A thing that is a lot like ES6 `Map`, but without iterators, for use 4in environments where `for..of` syntax and `Map` are not available. 5 6If you need iterators, or just in general a more faithful polyfill to 7ES6 Maps, check out [es6-map](http://npm.im/es6-map). 8 9If you are in an environment where `Map` is supported, then that will 10be returned instead, unless `process.env.TEST_PSEUDOMAP` is set. 11 12You can use any value as keys, and any value as data. Setting again 13with the identical key will overwrite the previous value. 14 15Internally, data is stored on an `Object.create(null)` style object. 16The key is coerced to a string to generate the key on the internal 17data-bag object. The original key used is stored along with the data. 18 19In the event of a stringified-key collision, a new key is generated by 20appending an increasing number to the stringified-key until finding 21either the intended key or an empty spot. 22 23Note that because object traversal order of plain objects is not 24guaranteed to be identical to insertion order, the insertion order 25guarantee of `Map.prototype.forEach` is not guaranteed in this 26implementation. However, in all versions of Node.js and V8 where this 27module works, `forEach` does traverse data in insertion order. 28 29## API 30 31Most of the [Map 32API](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map), 33with the following exceptions: 34 351. A `Map` object is not an iterator. 362. `values`, `keys`, and `entries` methods are not implemented, 37 because they return iterators. 383. The argument to the constructor can be an Array of `[key, value]` 39 pairs, or a `Map` or `PseudoMap` object. But, since iterators 40 aren't used, passing any plain-old iterator won't initialize the 41 map properly. 42 43## USAGE 44 45Use just like a regular ES6 Map. 46 47```javascript 48var PseudoMap = require('pseudomap') 49 50// optionally provide a pseudomap, or an array of [key,value] pairs 51// as the argument to initialize the map with 52var myMap = new PseudoMap() 53 54myMap.set(1, 'number 1') 55myMap.set('1', 'string 1') 56var akey = {} 57var bkey = {} 58myMap.set(akey, { some: 'data' }) 59myMap.set(bkey, { some: 'other data' }) 60``` 61