Flyweight

flyweight.js

var Flyweight = function() {
	this._all = null;
	this._indexed = null;
};

Flyweight.prototype._fetch = function() {
	console.log('fetch');
	return Promise.resolve([{
		_id: 1
	}]);
};

Flyweight.prototype.findAll = function() {
	if (this._all) {
		return Promise.resolve(this._all);
	} else {
		return this._fetch().then(function(all) {
			this._all = all;
			return Promise.resolve(this._all);
		}.bind(this));
	}
};
Flyweight.prototype._indexedAll = function() {
	if (this._indexed) {
		return Promise.resolve(this._indexed);
	}
	return this.findAll().then(function() {
		var all = this._all;
		this._indexed = {};
		for (var i = 0; i < all.length; i++) {
			this._indexed[all[i]._id] = all[i];
		}
		return Promise.resolve(this._indexed);
	}.bind(this));
};

Flyweight.prototype.find = function(id) {
	return this._indexedAll().then(function(indexed) {
		return Promise.resolve(indexed[id]);
	});
};

Flyweight.prototype.reset = function(id) {
	this._all = null;
	this._indexed = null;
};

var fw = new Flyweight()
fw.find(2).then(function(obj) {
	console.log(obj);
	fw.find(1).then(function(obj) {
		console.log(obj);
	});
});