<html>
<head>
<script src="https://libs.baidu.com/jquery/1.10.2/jquery.min.js">
</script>
<script>
$(document).ready(function(){
$("button").click(function(){
var btn = $(this).text();
$("p").css("background-color","white");
$("p" + btn).css("background-color","yellow");
});
});
</script>
</head>
<body>
<h1>This is a heading in body</h1>
<p>The first paragraph in body.</p>
<p>The second paragraph in body.</p>
<div style="border:1px solid;">
<span>This is a span element in div</span>
<p>The first paragraph in div.</p>
<p>The second paragraph in div.</p>
<p>The third paragraph in div.</p>
<p>The last paragraph in div.</p>
<span>This is a span element in div</span>
</div><br>
<div style="border:1px solid;">
<p>The first paragraph in another div.</p>
<p>The second paragraph in another div.</p>
<p>The last paragraph in another div.</p>
</div>
<p>The last paragraph in body.</p>
<button>:nth-child(2)</button>
<button>:nth-last-child(2)</button>
<button>:nth-of-type(2)</button>
<button>:nth-last-of-type(2)</button>
</body>
</html>