@psenger/bidirectional-map

Bidirectional key-value lookup — set once, look up from either side in O(1).

Features • Installation • Quick Start • API • Contributing

A standard JavaScript Map only goes one direction. BiDirectionalMap registers both A→B and B→A in a single set() call — so get(A) returns B and get(B) returns A without managing a second structure yourself. It extends the native Map, so every method you already use (get, has, delete, forEach, iteration) works without modification. Zero runtime dependencies.

Features

• One call, both directions. map.set(key, value) registers the forward and reverse mapping automatically — no second set() needed.
• Consistent pairs. Assigning a key that already participates in a relationship removes the stale pair first, keeping the map internally consistent.
• Full Map compatibility. Extends the built-in Map — spread, destructuring, entries(), keys(), values(), and size all work as-is.

Installation

npm install @psenger/bidirectional-map--save

or

yarn add @psenger/bidirectional-map

Example Usage

const bidiMap = new BiDirectionalMap();
bidiMap.set(1, 2).set(3, 4);
console.log (`Key(1) = Value(${bidiMap.get(1)})` );
console.log (`Key(2) = Value(${bidiMap.get(2)})` );
console.log (`Key(3) = Value(${bidiMap.get(3)})` );
console.log (`Key(4) = Value(${bidiMap.get(4)})` );
// Key(1) = Value(2)
// Key(2) = Value(1)
// Key(3) = Value(4)
// Key(4) = Value(3)
for( let [Key,Value] of bidiMap.entries()){
    console.log(`Key(${Key}) = Value(${Value})`);
}
// Key(1) = Value(2)
// Key(2) = Value(1)
// Key(3) = Value(4)
// Key(4) = Value(3)

API

BiDirectionalMap

{BiDirectionalMap}

Kind: global class
See: wikipedia for further information
Version: 1.0.6

• BiDirectionalMap
  • new BiDirectionalMap([props])
  • instance
    • .set(key, value) ⇒ BiDirectionalMap
  • static
    • .Symbol.species ⇒ MapConstructor

new BiDirectionalMap([props])

| Param | Type | Description | | --- | --- | --- | | [props] | Iterable | An Iterable object whose elements are key-value pairs (arrays with two elements, e.g. [[ 1, ['one','two'] ],[ 2, ['three'] ]]). Each key-value pair is added to the new Map; null values are treated as undefined. |

biDirectionalMap.set(key, value) ⇒ BiDirectionalMap

Sets the value for the key in the Map object. Overriding the parent set and returns the Map object. Only works with String or `Numbers.

Kind: instance method of BiDirectionalMap

| Param | Type | Description | | --- | --- | --- | | key | string | number | The key of the element to add to the BiDirectionalMap object. | | value | string | number | The value of the element to add to the BiDirectionalMap object. |

BiDirectionalMap.Symbol.species ⇒ MapConstructor

Overwrite BiDirectionalMap species to the parent Map constructor

Kind: static property of BiDirectionalMap

License

MIT License

Copyright (c) 2021 Philip A Senger

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

A minimal, zero-dependency bidirectional Map for JavaScript and Node.js.

Report a bug • Contributing • npm