I read here that the main reason for using client side validation is:
the user can correct every field before they submit the form
This (sort of) assumes Ajax, but if the client side validation consists purely of Javascript, is there really a point to it anymore? It's easy enough to point out specific mistakes and store form data on refresh from PHP / Django / node.js, so if the client side script isn't pointing out mistakes as the user is making them, does it really make sense both from a UI and developer perspective to take the time to write that bit of code?