requestAnimationFrame polyfill

requestAnimationFrame.js

// http://paulirish.com/2011/requestanimationframe-for-smart-animating/
// http://my.opera.com/emoller/blog/2011/12/20/requestanimationframe-for-smart-er-animating

// requestAnimationFrame polyfill by Erik Möller
// fixes from Paul Irish and Tino Zijdel
// perf improvements by Stephen McKamey

(function(window) {
	'use strict';

	/**
	 * vendor prefixes
	 * @type {Array}
	 */
	var vendors = ['webkit', 'moz', 'ms', 'o'];
	while (vendors.length && !window.requestAnimationFrame) {
		/**
		 * next vendor prefix to test
		 * @type {String}
		 */
		var prefix = vendors.pop();
		window.requestAnimationFrame = window[prefix+'RequestAnimationFrame'];
		window.cancelAnimationFrame = window[prefix+'CancelAnimationFrame'] ||
				window[prefix+'CancelRequestAnimationFrame'];
	}

	if (!window.requestAnimationFrame) {
		/**
		 * cap the framerate at 60Hz
		 * @const
		 * @type {number}
		 */
		var DELAY = 1000/60;

		/**
		 * ID of the last tween
		 * @type {number}
		 */
		var _id = 0;

		/**
		 * Timestamp of last call
		 * @type {number}
		 */
		var _last = 0;

		window.requestAnimationFrame =
			/**
			 * @param callback {function} the animation tweening
			 */
			function(callback) {
				var now = +(new Date());
				var delay = Math.max(0, DELAY - (now - _last));
				_last = now + delay;
				return (_id = setTimeout(callback, delay));
			};
	}

	if (!window.cancelAnimationFrame) {
		window.cancelAnimationFrame = function(id) {
			clearTimeout(id);
		};
	}

}(window));