<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<title></title>
<!--jQuery1.81-->
<script type="text/javascript" src="../../js/jquery.min.js"></script>
<script type="text/javascript">
$(function () {
$('input:first').click(function(){
$("ul li:last").html(function (index, oldhtml) {
return "<a href='#'>" + index + "</a>"
});
});
});
</script>
</head>
<body>
<ul>
<li>1</li>
<li>2</li>
<li>3</li>
<li>4</li>
<li>5</li>
</ul>
<input type="button" value="Click"/>
</body>
</html>
why the result of index isn't 4,but 0.