<html>
<head>
<script src="https://libs.baidu.com/jquery/1.10.2/jquery.min.js">
</script>
<script>
$(document).ready(function(){
$("button").click(function(){
$("li").removeClass(function(n) {
if (n==0||n==1) {return "listitem"}
else {return ""}
});
});
});
</script>
<style type="text/css">
.listitem
{
color:red;
}
</style>
</head>
<body>
<h1>This is a heading</h1>
<ul>
<li class="listitem">Peter</li>
<li class="listitem">Lois</li>
<li class="listitem">Chris</li>
<li class="listitem">Stewie</li>
</ul>
<button>Remove class "listitem" from the li elements with index 0 and 1</button>
</body>
</html>