piratemap

An extension of the builtin Map class, but the keys are compared by value instead of reference.

Installation

npm install piratemap

Why would I use this?

If you want to use an object as a key in a Map - unless you keep a reference to the original object, you will not be able to easily retrieve the value, or you might also accidentally insert duplicate items.

PirateMap provides has, get, set and delete methods that check if a key with the same value already exists in the map.

Why would I not use this?

If you care about high performance, you may not want to use this library - instead try and find a way to serialize your keys as strings.

Examples

With a regular map, you can use an object as a key -- but it may not work as you would expect:

const map = new Map()

const key = { x: 4, y: 7 }

map.set(key, 'here be treasure')
map.get(key) // 'here be tresure'

// however, if you try and access the map with a similar object...
map.get({ x: 4, y: 7 }) // undefined :(

With PirateMap, this is not an issue!

import { createPirateMap } from 'piratemap'

type Coordinates = { x: number, y: number }
const pirateMap = createPirateMap<Coordinates>((a, b) => {
    return a.x === b.x && a.y === b.y
})

const map = new Map()

pirateMap.set(map, {x: 4, y: 7}, 'here be treasure')

pirateMap.get(map, {x: 4, y: 7}) // 'here be treasure' :)

How do I use it?

Use createPirateMap with own equality function, or use a library like shallow-equal.

import { createPirateMap } from 'piratemap'

type Key = {
    id: number
    rangeStart: number
    rangeEnd: number
}

const pirateMap = createPirateMap<Key>((a, b) => {
    return (
        a.id === b.id &&
        a.rangeStart === b.rangeStart &&
        a.rangeEnd === b.rangeEnd
    )
})

const map = new Map<Key, Value[]>()

pirateMap.set(map, { id, rangeStart, rangeEnd }, values[])
pirateMap.get(map, { id, rangeStart, rangeEnd })

API

The API mimics methods on the built-in Map class.

get

const map = new Map([
    [[1, 2, 3], 'value']
])

pirateMapArray.get(map, [1, 2, 3]) // value
pirateMapArray.get(map, [4, 5, 6]) // undefined

has

const map = new Map([
    [[1, 2, 3], 'value']
])

pirateMapArray.has(map, [1, 2, 3]) // true
pirateMapArray.has(map, [4, 5, 6]) // false

set

const map = new Map([
    [[0, 1], '0-1']
    [[1, 2], '1-2']
])

pirateMapArray.set(map, [1, 2], 'new value')

[...map.entries()] // [ [[0, 1], '0-1'], [[1, 2], 'new value'] ]

delete

const map = new Map([
    [[0, 1], '0-1']
    [[1, 2], '1-2']
])

pirateMapArray.delete(map, [1, 2])

[...map.entries()] // [ [[0, 1], '0-1'] ]

License

PirateMap is licensed under the MIT License.