closest返回一个或0个结果？
下述代码第一个按钮点击后返回了两个结果，不是应该一个或0个结果么？
<!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: 350px;
height: 150px;
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>closest方法()</h2>
<div class="left first-div">
<div class="div">
<ul class="level-2">
<li class="item-a">A</li>
<li class="item-1">B
<ul class="level-3">
<li class="item-1">1</li>
<li class="item-2">2</li>
<li class="item-3">3</li>
</ul>
</li>
<li class="item-c">C</li>
</ul>
</div>
</div>
<br/>
<button>点击：closest传递选择器 </button>
<button>点击：closest传递一个元素对象</button>
<script type="text/javascript">
$("button:first").click(function() {
$("li.item-1").closest($("li.item-1"))
.css('border', '1px solid red');
})
</script>
<script type="text/javascript">
$("button:last").click(function() {
var itemB = $('.item-b')
$('li.item-1')
.closest(itemB)
.css('border', '1px solid blue');
})
</script>
</body>
</html>
