利用JS给博客网站左上角显示FPS帧数

$('body').before('');
var showFPS = (function(){
var requestAnimationFrame =
window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimationFrame ||
function(callback) {
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 );
};
appendFps = function(fps){
console.log(fps+'FPS');
$('#fps').html(fps+'FPS');
};
step();
})();

var console={};
    console.log=function(){};