此方法用于在选择器的基础之上精确筛选出第一个(最后一个)元素(可以使用前导限制范围):
实例:
<!DOCTYPE html>
<html lang='zh-cn'>
<head>
<title>Insert you title</title>
<meta http-equiv='description' content='this is my page'>
<meta http-equiv='keywords' content='keyword1,keyword2,keyword3'>
<meta http-equiv='Content-Type' content='text/html; charset=utf-8'>
<script type='text/javascript' src='./js/jquery-1.12.1.min.js'></script>
<style type='text/css'>
</style>
<script type='text/javascript'>
$(function(){
$('li').each(function(index){
$(this).html(index);
});
alert($('li').first().html()); //0
alert($('li').last().html()); //3
});
</script>
</head>
<body>
<div id='demo'>
<ul id='list'>
<li></li>
<li></li>
<li></li>
<li></li>
</ul>
</div>
</body>
</html>