/** ** 得到浏览器每秒帧数fps ** ** @Date Mar 13 2013 **/ var showFPS = (function(){ var requestAnimationFrame = window.requestAnimationFrame || //Chromium window.webkitRequestAnimationFrame || //Webkit window.mozRequestAnimationFrame || //Mozilla Geko window.oRequestAnimationFrame || //Opera Presto window.msRequestAnimationFrame || //IE Trident? function(callback) { //Fallback function window.setTimeout(callback, 1000/60); }; var e,pe,pid,fps,last,offset,step,appendFps; fps = 0; last = Date.now(); step = function(){ offset = Date.now() - last; fps += 1; if( offset >= 1000 ){ last += offset; appendFps(fps); fps = 0; } requestAnimationFrame( step ); }; //显示fps; 如果未指定元素id，默认<body>标签 appendFps = function(fps){ if(!e) e=document.createElement('span'); pe=pid?document.getElementById(pid):document.getElementsByTagName('body')[0]; e.innerHTML = "fps: " + fps; pe.appendChild(e); } return { setParentElementId : function(id){pid=id;}, go : function(){step();} } })();
