I use a lot of javascript for client-side scripting, putting it into .js file and then adding script tags as follows:
<script src=”js/myclient-side.js”></script>
In all modern browsers the javascript files and the style sheets are cached to improve performance. The page load time is hugely minimized due to caching but it has a pitfall (for programmers), when you make a new deployment on the server with huge changes to a javascript file, the file is not downloaded on the client side as it is used from the local cache. There are many workarounds to this pitfall, the simplest one that i feel is as follows:
<script src=”js/myclient-side.js?v=1“></script>
by just adding “?v=1” the browser will download the javascript file and replace it in the cache, for the next new deployment you can increase the number like v=2, v=3 … etc.