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61 lines
2.1 KiB
Markdown
61 lines
2.1 KiB
Markdown
5 years ago
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# pseudomap
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A thing that is a lot like ES6 `Map`, but without iterators, for use
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in environments where `for..of` syntax and `Map` are not available.
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If you need iterators, or just in general a more faithful polyfill to
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ES6 Maps, check out [es6-map](http://npm.im/es6-map).
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If you are in an environment where `Map` is supported, then that will
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be returned instead, unless `process.env.TEST_PSEUDOMAP` is set.
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You can use any value as keys, and any value as data. Setting again
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with the identical key will overwrite the previous value.
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Internally, data is stored on an `Object.create(null)` style object.
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The key is coerced to a string to generate the key on the internal
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data-bag object. The original key used is stored along with the data.
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In the event of a stringified-key collision, a new key is generated by
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appending an increasing number to the stringified-key until finding
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either the intended key or an empty spot.
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Note that because object traversal order of plain objects is not
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guaranteed to be identical to insertion order, the insertion order
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guarantee of `Map.prototype.forEach` is not guaranteed in this
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implementation. However, in all versions of Node.js and V8 where this
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module works, `forEach` does traverse data in insertion order.
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## API
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Most of the [Map
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API](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map),
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with the following exceptions:
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1. A `Map` object is not an iterator.
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2. `values`, `keys`, and `entries` methods are not implemented,
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because they return iterators.
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3. The argument to the constructor can be an Array of `[key, value]`
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pairs, or a `Map` or `PseudoMap` object. But, since iterators
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aren't used, passing any plain-old iterator won't initialize the
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map properly.
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## USAGE
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Use just like a regular ES6 Map.
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```javascript
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var PseudoMap = require('pseudomap')
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// optionally provide a pseudomap, or an array of [key,value] pairs
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// as the argument to initialize the map with
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var myMap = new PseudoMap()
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myMap.set(1, 'number 1')
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myMap.set('1', 'string 1')
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var akey = {}
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var bkey = {}
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myMap.set(akey, { some: 'data' })
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myMap.set(bkey, { some: 'other data' })
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```
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