A demo of using jQuery addClass method

The Code

Output

<!DOCTYPE html>
<html>
<head>
<script src="https://code.jquery.com/jquery-1.10.1.min.js"></script>

<script>
$(document).ready(function(){
  $("#btn_cls").click(function(){
    $("#class_demo").addClass("addcls");
  });
});
</script>
<style>

.addcls
{
  background: #232F36;
  font-size:16px;
  width:300px;
  height:50px;
  border-radius:10px;
  color:#fff;   
}
 

</style>
</head>
<body>

<div id="class_demo">A demo of adding class by jQuery</div>
<p>
<button id="btn_cls">Click here to addClass</button>
</p>
</body>
</html>

A demo of adding class by jQuery