Simple-BiMap

A tiny implementation of a Bidirectional Map in JavaScript, using Proxies. Aim of the library is to allow for simple selection/deletion with basic JavaScript object operators, with fallback functions to assign objects and functions as keys. Works with node v0.10+, although only fallback functions are available until v6+.

usage

define BiMap = require("./simple-bimap"); in Node.js or link to simple-bimap.js in the browser.

To use, just instantiate a new object:

var bimap = newBiMap();

primitive values

To assign a property bidirectional, just assign the property regularly or use _set():

bimap.a = 3; // set via operator/Proxy

bimap._set("b", 4) // set via fallback function

To get a value, just fetch the value as usual or use the _get operator:

console.log(bimap.a);          // "3"
console.log(bimap._get(3));    // "a"

console.log(bimap._get("b"));  // "4"
console.log(bimap[4]);         // "b"

advanced: functions and objects

You can assign functions and objects as values without issues:

function get5(){ return 5 }

bimap.get5 = get5;

var someObj = {x:1, y:2};
bimap.someObj = someObj;

console.log(bimap.get5());    // 5
console.log(bimap.someObj.x); // 1

But since JavaScript converts attribute selectors to Strings (and objects as keys to the dreaded "[object Object]"), you have to use the fallback functions for setting/getting functions and objects as keys:

function get10(){ return 2 * get5() }
function get20(){ return 4 * get5() }

//bimap[get10] = get20; //this does not work, get10 will not be a function
bimap._set(get10, get20); // this does

// functions work as selectors though
console.log(bimap[get10]()); // 20

// with objects, it's not that easy:
var anotherObj = {z:3};
var oneMoreObj = {w:4};
bimap._set(anotherObj, oneMoreObj);

// console.log(bimap.[anotherObj]);   // this is undefined
console.log(bimap._get(anotherObj));  // this works: "{ w: 4 }"

test

run node test.js to test in the node version of your choice.