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