<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<script src="js/jquery.js"></script>
<script>
window.onload = function(){
document.getElementById('btnok').onclick = function(){
//1.匹配索引为3的子元素
//$('li:nth-child(3)').html('test');
//2.匹配第一个子元素
//$('li:first-child').html('test');
//3.匹配值具有一个子元素的元素
$('li:only-child').html('test');
}
}
</script>
</head>
<body>
<input type="button" id="btnok" value="匹配" />
<hr>
<ol>
<li>AAAAA</li>
<li>BBBBB</li>
<li>CCCCC</li>
</ol>
<hr>
<ol>
<li>DDDDD</li>
</ol>
</body>
</html>