Sprite Sheets - Building JavaScript Games for Phones, Tablets, and Desktop - page 247

set: function (value) {
if (value >=0 && value < this.sprite.nrSheetElements)
this._sheetIndex = value;
}
});
Look at the SpriteGameObject.js file in the PenguinPairs1 example to see a few other examples
of properties you can add. The final method of SpriteGameObject is draw , which is simple because
most of the work has already been done in the SpriteSheet class:
SpriteGameObject.prototype.draw = function () {
if (this._visible)
this.sprite.draw(this.worldPosition, this.origin, this._sheetIndex);
};
Finalizing the Example
In the PenguinPairs1 example, you draw a background and a penguin on the screen (see Figure 18-2 ).
To test your new SpriteGameObject class, modify the currently selected sheet index by pressing the
left and right arrow buttons. This is done easily in the PenguinPairsGameWorld class:
if (Keyboard.pressed(Keys.left))
this.penguin.sheetIndex--;
else if (Keyboard.pressed(Keys.right))
this.penguin.sheetIndex++;