jsp测试函数的运行速度方法

// 时间转为时间戳（毫秒）
function time2stamp(){
  var d = new Date();
  return Date.parse(d)+d.getMilliseconds();
}

var t1 = time2stamp();
// 比较各游览器的DOM运行速度。
var divs = document.getElementByTagName("div"); 
var t2 = time2stamp();
alert("耗时：" + (t2 - t1) + " 毫秒");

var time1 = new Date
// 比较各游览器的DOM运行速度。
var divs = document.getElementByTagName("div"); 
alert("耗时：" + (new Date - time1) + " 毫秒");

!doctype html>
html dir="ltr" lang="zh-CN">
 head>
  meta charset="utf-8"/>
  title>类/title>
  script type="text/javascript" charset="utf-8">
   window.onload = function(){
 
    for (var i=0, elm; i4000; i++) {
     elm = document.createElement("div");
     elm.innerHTML = "第一重divdiv>第二重divdiv>第三重div/div>/div>";
     document.body.appendChild(elm);
    }
    document.getElementById("start-test").onclick = startTest;
    var uuid = 0;
    function startTest() {
     var divs = document.getElementsByTagName("div");
 
     var time1 = new Date();
     var i = -1, n = divs.length;while (++i  n) { 
       divs[i].uuid = uuid++;
     }
     document.getElementById("time-1").innerHTML = new Date() - time1;
 
     var time2 = new Date();
     var i = divs.length; while (--i >= 0) { 
      divs[i].uuid = uuid++;
     }
 
     document.getElementById("time-2").innerHTML = new Date() - time2;
 
     var time3 = new Date();
     for (var i=0, n=divs.length; in; i++) {
       divs[i].uuid = uuid++;
     }
     document.getElementById("time-3").innerHTML = new Date() - time3;
 
 
     var time4 = new Date();
     for (var n = divs.length - 1; n >= 0; n--) {
        divs[n].uuid = uuid++;
      }
     document.getElementById("time-4").innerHTML = new Date() - time4;
 
     var time5 = new Date();
     for (var n = divs.length - 1; n--;) {
        divs[n].uuid = uuid++;
      }
     document.getElementById("time-5").innerHTML = new Date() - time5;
 
     var time6 = new Date();
     var n = divs.length-1; do { 
       divs[n].uuid = uuid++;
     } while (n--);
     document.getElementById("time-6").innerHTML = new Date() - time6;

     var time7 = new Date();
     for(var i=0,el;el = divs[i++];){
      el.uuid = uuid++;
     };
     document.getElementById("time-7").innerHTML = new Date() - time7;
 
    }
   }
  /script>
 /head>
 body>
  style>
   h2 {
    margin:0;
    padding:10px;
    font-weight:500;
    font-size:13px;
    background:#8080C0;
    color:#fff;
   }
   p {
    margin:0;
    text-indent:2em;
    border-bottom:2px solid #a9ea00;
    background:#F2F1D7;
   }
   span.red{
    color:red;
   }
  /style>
  h1>JavaScript loop speed test/h1>
  ul>
   li>遍历页面上12000个DIV/li>
  /ul>
  input id="start-test" type="button" value="Start test">
  h2>循环1： var i = -1, n = divs.length;while (++i  n) { }span class="red">顺序/span>/h2>
  p id="time-1">/p>
 
  h2>循环2：var n = divs.length; while (--n >= 0) { }span class="red">倒序/span>/h2>
  p id="time-2">/p>
 
  h2>循环3：for (var i=0, n=divs.length; in; i++)span class="red">顺序/span>/h2>
  p id="time-3">/p>
 
  h2>循环4：for (var n = divs.length - 1; n >= 0; n--) { }span class="red">倒序/span>/h2>
  p id="time-4">/p>
 
  h2>循环5：for (var n = divs.length - 1; n--;) { }span class="red">倒序/span>/h2>
  p id="time-5">/p>
 
  h2>循环6： var n = divs.length-1; do { } while (n--)span class="red">倒序/span>/h2>
  p id="time-6">/p>

  h2>循环7： for(var i=0,el;el = divs[i++];){ } span class="red">顺序/span>/h2>
  p id="time-7">/p>
 /body>
/html>