How to call an external js file <script src="path_to_file/file_name.js"> for screen size less than 768px?

Question

I have a file with php Yii code, designed using bootstrap. In that, I require a particular external js file only for screen width 768px or less. How can I call the external js file for screen size less than 768px?

I have tried:
<div class="show-xs"> <script src="path_to_file/file_name.js"> </div>
Where the div is styled "display:none" upto 768px and "display:block" below 768px

Answer 1

Verified and working!

<script>
if (screen && screen.width < 768) {
  document.write('<script type="text/javascript" src="path_to_file/file_name.js"><\/script>');
}
</script>