<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 ----------> <div class="container"> <div class="row"> <form name="myForm" action="/action_page.php" onsubmit="return validateForm()" method="post"> Name: <input type="text" name="fname"> <input type="submit" value="Submit"> </form> </div> </div>

function validateForm() { var x = document.forms["myForm"]["fname"].value; if (x == "") { alert("Name must be filled out"); return false; }