var lastTime = Date.now(); 
var vendors = ['ms', 'moz', 'webkit', 'o'] ; 
for (var x = 0; 
x < _AN_Read_length('length', vendors) && !window.requestAnimationFrame; x++ ){ 
window.requestAnimationFrame = window[vendors[x] + 'RequestAnimationFrame']; 
window.cancelAnimationFrame = window[vendors[x] + 'CancelAnimationFrame'] || window[vendors[x] + 'CancelRequestAnimationFrame']; 
} 
if (!window.requestAnimationFrame) { 
window.requestAnimationFrame = function (callback){ 
if (typeof callback !== 'function') { 
throw new TypeError(callback + 'is not a function')
} 
var currentTime = Date.now(); 
var delay = 16 + lastTime - currentTime; 
if (delay < 0) { 
delay = 0; 
} 
lastTime = currentTime; 
return _AN_Call_settimeout('setTimeout', window, function (){ 
lastTime = Date.now(); 
callback(performance.now()); 
} 
, delay); 
} 
; 
} 
if (!window.cancelAnimationFrame) { 
window.cancelAnimationFrame = function (id){ 
clearTimeout(id); 
} 
; 
}