<!DOCTYPE html>
<html>
<head>
<script src="https://libs.baidu.com/jquery/2.1.4/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>
.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>