<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css"> <script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script> <script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script> <!------ Include the above in your HEAD tag ----------> <p>The sample code demonstrates how to use the <strong><a href="https://www.androidaura.com/javascript/javascript-indexof">JavaScript array indexOf() method</a></strong>. It expects a numeric argument and returns the first index in an array at which a specific value or data element is found.</p>