jQuery traversal - filtering
Abbreviation range of search elements
The three most basic filtering methods are: first(), last () and eq(), which allow you to select a specific element based on its position within a set of elements.
Other filtering methods, such as filter() and not() allow you to select elements that match or do not match a specified criterion.
jQuery first() method
first() method returns the first element of the selected element.
The following example selects the first <p> element inside the first <div> element:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src="http://libs.baidu.com/jquery/1.10.2/jquery.min.js">
</script>
<script>
$(document).ready(function(){
$("div p").first().css("background-color","yellow");
});
</script>
</head>
<body>
<h1>欢迎访问我的主页</h1>
<div>
<p>这是 div 中的一个段落。</p>
</div>
<div>
<p>这是另外一个 div 中的一个段落。</p>
</div>
<p>这是一个段落。</p>
</body>
</html>Run the program and try it
jQuery last() method
last() method returns the last element of the selected element.
The following example selects the last <p> element in the last <div> element:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src="http://libs.baidu.com/jquery/1.10.2/jquery.min.js">
</script>
<script>
$(document).ready(function(){
$("div p").last().css("background-color","yellow");
});
</script>
</head>
<body>
<h1>欢迎访问我的主页</h1>
<div>
<p>这是 div 中的一个段落。</p>
</div>
<div>
<p>这是另外一个 div 中的一个段落。</p>
</div>
<p>这是一个段落。</p>
</body>
</html>Run the program and try it
jQuery eq() method
eq() method returns the element with the specified index number among the selected elements.
The index number starts from 0, so the index number of the first element is 0 instead of 1. The following example selects the second <p> element (index number 1):
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src="http://libs.baidu.com/jquery/1.10.2/jquery.min.js">
</script>
<script>
$(document).ready(function(){
$("p").eq(1).css("background-color","yellow");
});
</script>
</head>
<body>
<h1>欢迎访问我的主页</h1>
<p>php中文网 (index 0).</p>
<p>//m.sbmmt.com (index 1)。</p>
<p>google (index 2).</p>
<p>http://www.google.com (index 3)。</p>
</body>
</html>Run the program to try it
jQuery filter() method
The filter() method allows you to specify a criterion. Elements that do not match this criterion are removed from the collection, and matching elements are returned.
The following example returns all <p> elements with the class name "url":
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src="http://libs.baidu.com/jquery/1.10.2/jquery.min.js">
</script>
<script>
$(document).ready(function(){
$("p").filter(".url").css("background-color","yellow");
});
</script>
</head>
<body>
<h1>欢迎访问我的主页</h1>
<p>php中文网 (index 0).</p>
<p class="url">//m.sbmmt.com (index 1)。</p>
<p>google (index 2).</p>
<p class="url">http://www.google.com (index 3)。</p>
</body>
</html>Run the program to try it
jQuery not() method
not() method returns all elements that do not match the criteria.
Tip: The not() method is the opposite of filter().
The following example returns all <p> elements without the class name "url":
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src="http://libs.baidu.com/jquery/1.10.2/jquery.min.js">
</script>
<script>
$(document).ready(function(){
$("p").not(".url").css("background-color","yellow");
});
</script>
</head>
<body>
<h1>欢迎访问我的主页</h1>
<p>php中文网 (index 0).</p>
<p class="url">//m.sbmmt.com (index 1)。</p>
<p>google (index 2).</p>
<p class="url">http://www.google.com (index 3)。</p>
</body>
</html>Run the program to try it
