Lazy singleton with BackboneJS

Question

I am trying to have a Backbone.Model which is a singleton and I wish to instantiate it lazily. I only need to support modern browsers so please do not worry about the use of ES5 getter.

Is this the simplest way of achieving my goal?

var LazySingleton = function(){
 var _LazySingleton = Backbone.Model.extend({
 defaults: {
 foo: 0
 },
 initialize: function(){
 console.log('I am initializing');
 }
 });
 return {
 _instance: null,
 get instance() {
 if (this._instance === null) {
 this._instance = new _LazySingleton();
 }
 return this._instance;
 }
 };
}();
console.log('LazySingleton has been declared, but not initialized');
LazySingleton.instance.set('foo', 3); 
console.log('foo should be 3:', LazySingleton.instance.get('foo'));

Answer 1

This is not the simplest way.

• There seems to be no point in instance, if there can be only 1 instance, why have it all ?
• Why have initialize at all ?
• Why set foo to 0, I would set it undefined

• If I were to keep the instance concept, I would write this:

  _instance: null,
  get instance() {
   if (this._instance === null) {
   this._instance = new _LazySingleton();
   }
   return this._instance;
  }
  

  as

  _instance: null,
  get instance() {
   return this._instance = this._instance || new _LazySingleton();
  }
  

I would probably go for something like this ( I might have the syntax wrong )

var LazySingleton = Backbone.Model.extend({
 defaults: {
 foo: undefined
 },
 initialize: function(){
 });