Tryit Editor v2.9

Edit This Code:
<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.2/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>
.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>