一段效率很高的for循環語句使用方法
2019-11-21 01:58:40
供稿：網友
給表格的每行加上樣式，注意for的第二個參數，當數組下標越界時，row=row[i]返回false，到此循環結束。
var rows = document.getElementsByTagName('tr');
for( var i = 0, row; row = rows[i]; i++ ) {
row.className = 'newclass';
}
測試代碼：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>無標題文檔</title>
<style>
li { margin-left:28px;}
.abc {background-color:#eee;font-size:14px; margin-bottom:10px;}
</style>
<SCRIPT LANGUAGE="JavaScript">
<!--
function a(){
var row = document.getElementsByTagName("li");
var t1 = new Date();
for (var i=0,j; j=row[i]; i++)
{
j.className="abc";
}
var t2 = new Date();
alert("耗時 "+(t2-t1).toString()+" 毫秒");
}
function b(){
var row = document.getElementsByTagName("li");
var t1 = new Date();
for (var i=0; i<row.length; i++)
{
row[i].className="abc";
}
var t2 = new Date();
alert("耗時 "+(t2-t1).toString()+" 毫秒");
}
function c(){
var j="<ol>";
for (var i=0; i<2000; i++)
{
j=j+"<li>測試文字</li>";
}
j=j+"</ol>";
document.getElementById("box").innerHTML = j;
}
//-->
</SCRIPT>
</head>
<BODY>
<input type="button" value="CreateTable" onclick="c()" />
<input type="button" value="Test old method!" onclick="b()" />
<input type="button" value="Test new method!" onclick="a()" />
<input type="button" value="Clear" onclick="document.getElementById('box').innerHTML='';" />
<div id="box"></div>
</BODY>
</HTML>
