I'm just starting out in the journey of front-end development as a hobby and have been doing server-side infrastructure automation for my career for almost a decade now - so please bear that in mind with might seem like an ignorant question.

Let's say I have the client-side pick up the bill for logic/computing for form validation. Now for security reasons would I also want validation on the server-side as well due to the fact that client-side JavaScript can be manipulated? Or am I totally off-base in this line of thinking.

I'm personally opposed to how much logic happens on the client-side but I'm open to having conversation and changing my opinion on that.