html
<!DOCTYPE html>
<html>
<head>
<title>JQuery Demo</title>
<script src="jquery.min.js"></script>
<script src="script.js"></script>
<style>
.selected {
background-color: yellow;
}
</style>
</head>
<body>
<div id="myDiv">Hello, JQuery!</div>
<button id="myButton">Change Style</button>
</body>
</html>
script
$(document).ready(function() {
$('#myButton').click(function() {
$('#myDiv').addClass('selected');
});
});
