CODE EXAMPLE FOR JAVASCRIPT

jquery mobile or desktop

<script>
$(document).ready(function(){
    if (window.matchMedia('(max-width: 767px)').matches) {
      // The viewport is less than 768 pixels wide
      alert('This is a mobile device.');
    } else {
      // The viewport is at least 768 pixels wide
      alert('This is a tablet or desktop.');
    }
});
</script>