piratemap
v5.0.0
Published
ES6 Map, but the keys are compared by value instead of reference.
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138
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Readme
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.