子比美化-网站左上角添加 FPS 帧率显示

// FPS 帧开始
$('body').before('<div id="fps" style="z-index:10000;position:fixed;top:3;left:3;font-weight:bold;"></div>');
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();
})();
// FPS 帧结束