A highly efficient for loop statement usage _javascript tips

Source: Internet
Author: User
Add a style to each row of the table, note the second argument for, and when the array subscript crosses over, Row=row[i] returns false to the end of the loop.

var rows = document.getElementsByTagName (' tr ');
for (var i = 0, row; row = rows[i]; i++) {
Row.classname = ' Newclass ';
Test code:

<! DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 transitional//en" "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd ">
<meta http-equiv= "Content-type" content= "text/html; charset=gb2312 "/>
<title> Untitled Document </title>
Li {margin-left:28px;}
. ABC {background-color: #eee; font-size:14px; margin-bottom:10px;}
<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 ("Time-consuming" + (T2-T1). toString () + "millisecond");
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 ("Time-consuming" + (T2-T1). toString () + "millisecond");
Function C () {
var j= "<ol>";
for (var i=0; i<2000; i++)
j=j+ "<li> Test text </li>";
j=j+ "</ol>";
document.getElementById ("box"). InnerHTML = J;
<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>

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