Function that allows any object to function as a game rendering loop.

GameLoopTrait.js

/**
* Provides GameLoop Trait
*
* Based on: http://nokarma.org/2011/02/02/javascript-game-development-the-game-loop/
*
* @required EventEmitterTrait
* @module Traits
* @submodule GameLoopTrait
*/
var GameLoopTrait = (function(EventEmiterTrait, requestAnimationFrame) {

/**
* @method GameLoopTrait
* @param instance {Object}
*/
function GameLoopTrait(instance)
{
	EventEmiterTrait(instance)
	var FPS = 60
	var loops = 0
	var skipTicks = 1000 / FPS
	var maxFrameSkip = 5
	var nextGameTick = Date.now()
	var animReference = null

	/**
	* @private
	* @method loop
	*/
	function loop()
	{		
		while(Date.now() > nextGameTick && loops < maxFrameSkip)
		{
			instance.emit('update')
			nextGameTick += skipTicks
			loops++
		}
		
		if (loops)
		{
			instance.emit('render')
			loops = 0
		}

		animReference = requestAnimationFrame(loop)
	}

	/**
	* @method start
	*/
	Object.defineProperty(instance, 'start', {
		configurable: false, enumerable: true,
		value: function GameLoopTrait__start()
		{
			animReference = requestAnimationFrame(loop)
		}
	})

	/**
	* @method stop
	*/
	Object.defineProperty(instance, 'stop', {
		configurable: false, enumerable: true,
		value: function GameLoopTrait__stop()
		{
			if (animReference)
			{
				cancelAnimationFrame(animReference)
				animReference = null
			}
		}
	})
}

return GameLoopTrait
})(EventEmitterTrait, window.requestAnimationFrame);