OK, I'll admit I can sometimes be "late to the game" on some things.  Specifically, I realize that the whole arguments.callee/singleton design pattern/deprecation in Javascript debate is about two years old.  However, I think this is one of those things that generally is worth mentioning (and consequently giving more fuel  and attention to).

As many of you know, I started a new gig at VEVO this past June as a web developer.  In other words, I'm moving away from Actionscript and more towards Javascript.  Don't get me wrong; I'm still true to my AS3/PHP/OOP roots but JS is where it's at right now so I needed to make a change.  One of the things I needed to figure out first is how to convert my design patterns over to JS, specifically the infamous Singleton.  Given the fact that JS is a loosely typed language, this wasn't going to be easy.

After much research, I created the following example:

function SingletonClass(nme,clr){ if (arguments.callee.instance){return arguments.callee.instance;} arguments.callee.instance = this; this.name = nme; this.color = clr; } SingletonClass.prototype.setColor = function(clr){ this.color = clr; } SingletonClass.prototype.setName = function(nme){ this.name = nme; } var singleton1 = new SingletonClass('firstSingleton','black'); console.log('(singleton1): My name is ' + singleton1.name + ' and my color is ' + singleton1.color + '.'); var singleton2 = new SingletonClass('secondSingleton','green'); console.log('(singleton2): My name is ' + singleton2.name + ' and my color is ' + singleton2.color + '.'); singleton2.setColor('blue'); singleton2.setName('Matt'); console.log('(singleton1): My name is ' + singleton1.name + ' and my color is ' + singleton1.color + '.');

This works beautifully, with one small exception; arguments.callee has been deprecated.  If you're like me, you're immediately thinking, "WHAT?????" right about now.  After a bit of research, I found the following but reports:

https://bugzilla.mozilla.org/show_bug.cgi?id=725398

https://bugs.ecmascript.org/show_bug.cgi?id=263

However, this doesn't solve the problem.  The fact is, currently this is deprecated so if you want to create a true Singleton, a bit of adjustment is necessary.  Given that, I came up with the following:

var SingletonInstance; function SingletonClass(nme,clr){ if(SingletonInstance){return SingletonInstance;} SingletonInstance = this; this.name = nme; this.color = clr; } SingletonClass.prototype.setColor = function(clr){ this.color = clr; } SingletonClass.prototype.setName = function(nme){ this.name = nme; } var singleton1 = new SingletonClass('firstSingleton','black'); console.log('(singleton1): My name is ' + singleton1.name + ' and my color is ' + singleton1.color + '.'); var singleton2 = new SingletonClass('secondSingleton','green'); console.log('(singleton2): My name is ' + singleton2.name + ' and my color is ' + singleton2.color + '.'); singleton2.setColor('blue'); singleton2.setName('Matt'); console.log('(singleton1): My name is ' + singleton1.name + ' and my color is ' + singleton1.color + '.');