<html>
<head>
<script src="https://libs.baidu.com/jquery/1.10.2/jquery.min.js">
</script>
<script>
$(document).ready(function(){
$("button").click(function(){
$("p,h1").removeClass("head intro main");
});
});
</script>
<style type="text/css">
.head
{
font-size:2em;
color:green;
}
.intro
{
font-size:120%;
color:red;
}
.main
{
font-size:20px;
color:blue;
}
</style>
</head>
<body>
<h1 class="head">This is a heading</h1>
<p class="intro">This is a paragraph.</p>
<p class="main">This is another paragraph.</p>
<button>Remove the "head", "intro" and "main" class from the selected elements</button>
</body>
</html>