Simple dictionary with value equality for keys

dict.js

/**
 * Recursive object key sort for predictable JSON serialization
 */
function sortObject(obj) {
  if (!obj || typeof obj !== "object") return obj;
  if (Array.isArray(obj)) return obj.map(item => sortObject(item));
  return Object.keys(obj).sort().reduce((o, x) => (o[x] = sortObject(obj[x]), o), {});
}

/**
 * Predictable JSON serialization of an object
 */
function hash(obj) { return JSON.stringify(sortObject(obj)); }

/**
 * Simple class that wraps a Map with key serialization/deserialization
 */
class Dict {
  constructor() { this._map = new Map(); }
  get length()  { return this._map.length; }
  has(key)      { return this._map.has(hash(key)); }
  get(key)      { return this._map.get(hash(key)); }
  set(key, val) { this._map.set(hash(key), val); }
  *[Symbol.iterator]() {
    for (let [key, val] of this._map)
      yield [JSON.parse(key), val];
  }
}

/* Examples */
const d = new Dict();
d.set({ foo: 10 }, "Hi!");
d.get({ foo: 10 }); // Returns "Hi!"
for (const [k, v] of d) {
  // "k" is an object { foo: 10 }
  // "v" is "Hi!"
}