https://github.com/fregante/many-keys-map

A Map subclass with support for multiple keys for one entry.
https://github.com/fregante/many-keys-map

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A Map subclass with support for multiple keys for one entry.

• Host: GitHub
• URL: https://github.com/fregante/many-keys-map
• Owner: fregante
• License: mit
• Created: 2019-03-02T17:07:23.000Z (over 5 years ago)
• Default Branch: main
• Last Pushed: 2023-03-17T16:16:21.000Z (over 1 year ago)
• Last Synced: 2024-07-12T03:56:06.854Z (2 months ago)
• Language: JavaScript
• Size: 36.1 KB
• Stars: 107
• Watchers: 4
• Forks: 3
• Open Issues: 1
• Metadata Files:
  • Readme: readme.md
  • License: license

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README

        
# many-keys-map [![(size)][badge-gzip]](#no-link)

  [badge-gzip]: https://img.shields.io/bundlephobia/minzip/many-keys-map.svg?label=gzipped

  [link-npm]: https://www.npmjs.com/package/many-keys-map

> A `Map` subclass with support for multiple keys for one entry.

A `ManyKeysMap` object is identical to a regular `Map`, with the exception that it only supports a _sequence of keys_ as key, instead of a single key. This will let you attach a value to a specific combination of keys, instead of a single key.

```js

const regularMap = new Map();

regularMap.set('hello', true);

const manyKeysMap = new ManyKeysMap();

manyKeysMap.set(['hello', 'world'], true);

```

This is useful when the keys cannot be easily combined (i.e. object)

```js

const handlers = new ManyKeysMap();

handlers.set([element, 'click'], onClickFn);

handlers.set([element, 'keypress', {passive: true}], onKeypressFn);

// Since objects are stored by reference, it’s best to stringify `options` object like the above

handlers.set([element, 'keypress', JSON.stringify({passive: true})], onKeypressFn);

```

The number of keys allowed is unlimited and their order matters.

## Install

```

$ npm install many-keys-map

```

## Usage

It should work exactly the same as a `Map`, except that the `key` must always be an array.

```js

import ManyKeysMap from 'many-keys-map';

const groups = new ManyKeysMap();

groups.set([header, 'admin'], true);

groups.set([target, 'tools'], [1, 'any value is supported']);

const data = new ManyKeysMap([

	[['hello key'], 'value'],

	[[42, null], new Date()]

]);

data.get(['hello key']);

// => 'value'

data.get([42, null]);

// => date Object

data.get(['42']);

// => undefined

data.has([Symbol()]);

// => false

for (const [keys, value] of data) {

	console.log(keys);

	console.log(value);

}

// => ['hello key']

// => 'value'

// => [42, null]

// => date Object

```

### Allowed keys

1. Keys must always be an array, e.g. `.set([a, b], 'hello')`

2. Only the values in the `keys` array are stored, not the array itself — so future changes to the array won’t be reflected in the map.

3. `ManyKeysMap` supports any number of keys, any of these are valid and different: `.get([a])` and `.get([a, b, c, d, e, f, g])`

4. The order of keys matters, so `.get([a, b])` is different from `.get([b, a])`

5. The keys can be anything supported by `Map`.

# Related

- [many-keys-weakmap](https://github.com/fregante/many-keys-weakmap) - A `WeakMap` subclass with support for multiple keys for one entry.