<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>隔行变色</title>
<script>
window.onload = function () {
var aLi = document.getElementsByTagName('li');
for (var i = 0; i < aLi.length; i++) {
if (i % 2 == 0) {
aLi[i].style.background = '#333';
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aLi[i].style.background='red';
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<body>
<ul>
<li>2</li>
<li>2</li>
<li>2</li>
<li>2</li>
<li>2</li>
<li>1</li>
</ul> </body>
</html>