Button class with EaselJS

gistfile1.js

(function(k) {
    var Button = function(a, x, y) {
        this.initialize(a,x,y)
    },p = Button.prototype = new DisplayObject;

    p.left = 0;
    p.top = 0;
    p.ypos = 0;
    p.image = null;
    p.snapToPixel = true;
    p.DisplayObject_initialize = p.initialize;

    p.initialize = function(a,x,y) {
        this.DisplayObject_initialize();
        if (typeof a == "string") {
			this.image = new Image();
			this.image.src = a;
		} else {
			this.image = a;
		}
        this.top = y;
        this.left = x;
    };

    p.isVisible = function() {
        return this.visible && this.alpha > 0 && this.scaleX != 0 && this.scaleY != 0 && this.image && (this.image.complete || this.image.getContext || this.image.readyState == 2)
    };

    p.DisplayObject_draw = p.draw;
    p.draw = function(ctx, ignoreCache) {
        if (this.DisplayObject_draw(ctx, ignoreCache))return true;
        ctx.drawImage(this.image, 0,this.ypos, this.image.width, this.image.width, this.left, this.top, this.image.width, this.image.width);
        return true
    };

    p.clone = function() {
        var a = new Button(this.image, 0, 0);
        this.cloneProps(a);
        return a
    };

    p.toString = function() {
        return"[Button (name=" + this.name + ")]"
    };

    p.onMouseOver = function(){
        this.ypos = Math.floor(this.image.height/3);
    }
    p.onMouseOut = function() {
        this.ypos = 0;
    }
    p.onClick = function(){
        console.log("mousedown")
        this.ypos = Math.floor(this.image.height/3*2);
    }

    k.Button = Button
})(window);