Use of javascript Proxy for a new object relational concept in Javascript.

relate.js

let _instanceRelateDb = null;

class RelateDb {
  constructor() {
    if (_instanceRelateDb) { return _instanceRelateDb; }

    _instanceRelateDb = this;
    this._db = {};
  }

  set(relateId, relateObj) {
    this._db[relateId] = relateObj;
  }
  get(relateId) {
    return this._db[relateId];
  }
}

class RelateId {
  constructor(id) {
    this._id = id;
  }
  getId() {
    return this._id;
  }
}

function isRelateId(obj) {
  return obj && obj instanceof RelateId;
}

const handler = {
  get: function(obj, key) {
    let value = obj[key];
    if (isRelateId(value)) {
      return new RelateDb().get(value.getId());
    }
    return value;
  },
};

function relate(obj) {
  if (!obj.id) {
    obj.id = Symbol('__RELATE_ID__');
  }
  let relateObj = new Proxy(obj, handler);
  new RelateDb().set(obj.id, relateObj);

  return relateObj;
}

let first = relate({
  key: '1',
  nest: {
    key: '2',
  },
});
let second = relate({
  firstLn: new RelateId(first.id),
});

console.log(second.firstLn.key); // 1
console.log(second.firstLn.nest.key); // 2