Extending EaselJS Display Objects - Beginning HTML5 Games with CreateJS - page 177

Orb.prototype.Shape_initialize = Orb.prototype.initialize;
The orb's initialize function is then created. At the very least, this function needs to fire its super class's
initialize function, which is absolutely essential in order to fully extend all of the behavior of the class you are
extending. In other languages, this is equivalent to calling a super method inside a constructor function.
this.Shape_initialize();
Finally, the Orb class gets added to window so it is accessible throughout your application. Again, at this point this
Orb is nothing more than a Shape object. To make it unique, some custom properties and methods need to be added
to it. This was already done with the initialize function. This is done by using prototype .
Orb.prototype.initialize = function(){
};
You can similarly add properties to your custom class.
Orb.prototype.points = 4;
Let's put this all together to see the Orb class in completion, with the option to pass in a different color to each orb
(see Listing 8-2).
Listing 8-2. Sample Orb Class that Extends Shape
(function() {
var Orb = function(color) {
this.initialize(color);
}
Orb.prototype = new createjs.Shape();
Orb.prototype.Shape_initialize = Orb.prototype.initialize;
Orb.prototype.points = 4;
Orb.prototype.initialize = function(color) {
this.Shape_initialize();
this.graphics.beginFill(color).drawCircle(0,0,20);
}
Orb.prototype.die = function(){
createjs.Tween.get(this).to({alpha:0},100).call(function(e){
this.parent.removeChild(this);
});
}
window.Orb = Orb;
}());