javascript singleton question

Question

I just read a few threads on the discussion of singleton design in javascript. I\'m 100% new to the Design Pattern stuff but as I see since a Singleton by definition won\'t

Answer 1

The ES5 spec lets us use Object.create():

var SingletonClass = (function() {
    var instance;
    function SingletonClass() {
        if (instance == null) {
            instance = Object.create(SingletonClass.prototype);
        }

        return instance;
    }

    return {
        getInstance: function() {
            return new SingletonClass();
        }
   };
})();

var x = SingletonClass.getInstance();
var y = SingletonClass.getInstance();
var z = new x.constructor();

This is nice, since we don't have to worry about our constructor leaking, we still always end up with the same instance.

This structure also has the advantage that our Singleton doesn't construct itself until it is required. Additionally, using the closure as we do here prevents external code from using our "instance" variable, accidentally or otherwise. We can build more private variables in the same place and we can define anything we care to export publically on our class prototype.