A quick way to bust cache of scripts and style sheets in wordpress when debug is on (something you would most likely only be doing when in local development). Sets a new version number every time the page is releated based on the current Unix timestamp, otherwise return a set static number you can manualy update.
Example result in DEBUG mode:
<script type="text/javascript" src="http://localhost/wordpress.../js/scroll-to-top.js?ver=1447394696"></script>
Example result with DEBUG off:
<script type="text/javascript" src="http://localhost/wordpress.../js/scroll-to-top.js?ver=1.1"></script>
Source: