<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-type" content="text/html; charset=utf-8" />
<title></title>
<link rel="stylesheet" href="imooc.css" type="text/css">
<style>
.left {
width: auto;
height: 200px;
}
.left div {
width: 150px;
height: 70px;
padding: 5px;
margin: 5px;
float: left;
background: #bbffaa;
border: 1px solid #ccc;
}
.span {
color: blue;
}
</style>
<script src="http://lib.sinaapp.com/js/jquery/1.9.1/jquery-1.9.1.min.js"></script>
</head>
<body>
<h2>find方法()</h2>
<div class="left first-div">
<div class="div">
<ul class="level-1">
<li class="item-1">1</li>
<li class="item-2">2</li>
<li class="item-3">3</li>
</ul>
</div>
<div class="div">
<ul class="level-2">
<li class="item-1">1</li>
<li class="item-2 test">2</li>
<li class="item-3">3</li>
</ul>
</div>
<div class="div">
<ul class="level-3">
<li class="item-1">1</li>
<li class="item-2">2</li>
<li class="item-3">3</li>
</ul>
</div>
</div>
<button>点击：find传递表达式</button>
<br/>
<br/>
<h3>find表达式</h3>
<div style="border:1px solid red;">
<p>
<span>测试1</span>
<a>测试2</a>
</p>
<p>
<span>慕课网1</span>
<a>慕课网2</a>
</p>
<div>
<span>Aaron1</span>
<a>Aaron2</a>
</div>
</div>
<br/>
<br/>
<button>点击：find传递$对象</button>
<script type="text/javascript">
$("button:first").click(function() {
$(".left").find("li:last").css('border','1px solid red')
})
</script>
<script type="text/javascript">
$("button:last").click(function() {
//找到所有p元素，然后筛选出子元素是span标签的节点
//改变其字体颜色
var $spans = $('span');
$("p").find($spans).css('color', 'red');
})
</script>
</body>
</html>
为什么要写上这一步：var $spans = $('span');
