Two way key value hashmap/object/store in JavaScript. Get keys with values or values with keys.

twoWayKeyValueStore.js

/** 
 * Two way key value store.
 * When you want to get key with value or value with a key.
 * 
 * examples:
 * var store = twoWayKeyValueStore([ [200, "ok"], [401, "unauthorized"] ])
 * store.get(401) // "unauthorized"
 * store.get("unauthorized") // 401
 * store.set(200, "ok").get("ok") // 200
 * store.remove("ok").get(200) // undefined
 * obj = store.values() // { "200": "ok", ...
*/

export default function twoWayKeyValueStore(values) {
  var data = values ? values.reduce((obj, tuple) => {
    if (obj[tuple[1]] !== undefined) { throw new Error("duplicate key/value " + tuple[1]); }
    if (obj[tuple[0]] !== undefined) { throw new Error("duplicate key/value " + tuple[0]); }
    obj[tuple[1]] = tuple[0];
    obj[tuple[0]] = tuple[1];
    return obj;
  }, {}) : {};

  return {
    set: function(key, value) {
      if (data[key] !== undefined) { throw new Error("duplicate key/value " + key); }
      if (data[value] !== undefined) { throw new Error("duplicate key/value " + value); }
      data[key] = value;
      data[value] = key;
      return this;
    },
    get: function(key) {
      return data[key];
    },
    remove: function(key) {
      var value = data[key];
      data[value] = undefined;
      data[key] = undefined;
      return this;
    },
    values: function() { return data; }
  };
}