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"> <HTML> <HEAD> <TITLE> New Document </TITLE> <META 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;i<100;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> </HEAD> <BODY> <div id="container"></div> <input 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"> <HTML> <HEAD> <TITLE> New Document </TITLE> <META 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;i<100;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> </HEAD> <BODY> <div id="container"></div> <input 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]

createElement:

innerHTML:

运行代码框
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML> <HEAD> <TITLE> New Document </TITLE> <META 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;i<100;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> </HEAD> <BODY> <div id="container"></div> <input 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]

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