Sounds and Asset Management - Beginning HTML5 Games with CreateJS - page 208

Creating the Asteroid Class
Next, the asteroid sprite will be created. The Asteroid.js file contains the entire Asteroid class (see Listing 9-15).
Listing 9-15. The Asteroid Class - Asteroid.js
(function () {
window.game = window.game || {};
var Asteroid = function (spritesheet) {
this.initialize(spritesheet);
}
var p = Asteroid.prototype = new createjs.Sprite();
p.Sprite_initialize = p.initialize;
p.EXPLOSION_COMPLETE = 'explosion complete';
p.bounds = null;
p.speed = null;
p.initialize = function (spritesheet) {
this.Sprite_initialize(spritesheet);
var frame = this.speed = Math.floor(Math.random() * 4) + 1;
this.gotoAndStop('asteroid' + this.frame);
this.bounds = this.getBounds();
this.regX = this.bounds.width / 2;
this.regY = this.bounds.height / 2;
this.on('tick', this.move);
}
p.move = function (e) {
this.rotation += this.speed;
this.y += this.speed * 2;
if (this.y > canvas.height + this.bounds.height) {
this.y = -this.bounds.height;
}
}
p.explode = function () {
this.speed /= 2;
this.on('animationend', this.explosionComplete);
this.gotoAndPlay('explosion');
createjs.Sound.play(game.assets.EXPLOSION);
}
p.explosionComplete = function (e) {
this.stop();
this.dispatchEvent(this.EXPLOSION_COMPLETE);
}
window.game.Asteroid = Asteroid;
}());