javascript程序的执行效率问题

写了几年代码，很少谈到javascript程序的执行效率问题，今天就举几个例子看看，让大家看看程序优化是多么重要。
这节来看看createElement和innerHTML的表现。看看差别是多大

createElement:

运行代码框
!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"HTMLHEADTITLE New Document /TITLEMETA NAME="Generator" CONTENT="EditPlus"META NAME="Author" CONTENT=""META NAME="Keywords" CONTENT=""META NAME="Description" CONTENT=""script type="text/javascript"function init(){var staDate = new Date();var doc = window.document;for(var i=0;i100;i++){var oDiv = doc.createElement("div");var oText = doc.createTextNode("text");oDiv.appendChild(oText);container.appendChild(oDiv);oDiv.style.id = "div_"+i;oDiv.style.width = "100px";oDiv.style.height = "20px";oDiv.style.backgroundColor = "#eee";}alert(new Date - staDate);}/script/HEADBODYdiv id="container"/divinput type="button" value="start" onclick="init();" //BODY/HTML
[Ctrl+A 全部选择 提示：你可先修改部分代码，再按运行]

innerHTML:

运行代码框
!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"HTMLHEADTITLE New Document /TITLEMETA NAME="Generator" CONTENT="EditPlus"META NAME="Author" CONTENT=""META NAME="Keywords" CONTENT=""META NAME="Description" CONTENT=""script type="text/javascript"function init(){var staDate = new Date();var doc = window.document;for(var i=0;i100;i++){var str="div id='div_'"+i+"' style='width:100px; height:20px;background-color:#eee'test/div";container.innerHTML += str;}alert(new Date - staDate);}/script/HEADBODYdiv id="container"/divinput type="button" value="start" onclick="init();" //BODY/HTML
[Ctrl+A 全部选择 提示：你可先修改部分代码，再按运行]