It is very important for dynamic web applications, any js and css changes to become available to user (without need to refresh – reload browser page).
Instead of
<script type="text/javascript" src="index.js"></script>
use:
<script type="text/javascript" src="index.js?version=1"></script>
Everytime you modify JS file, use next version num (actually, you can use any other string, but ?version=n is more nice). So, you force user browser to retreive JS in case it is changed.
The same method can be applied for CSS.
Entrepreneur | Full-stack developer | Founder of MediSign Ltd. I have over 15 years of professional experience designing and developing web applications. I am also very experienced in managing (web) projects.