<!DOCTYPE html>
<html>
<head>
<script src="/lib/jquery-1.12.2.min.js"></script>
<script>
$(document).ready(function(){
    $("button").click(function(){
        $.ajax({url: "demo_ajax_script.js", dataType: "script"});
    });
});
</script>
</head>
<body>

<button>Use Ajax to get and then run a JavaScript</button>

</body>
</html>