An iPad is fine for writing code, but not capable of compiling/running code. For web development specifically you can't run a real web app on it. iOS Safari doesn't have the inspector/debugger so you can't use it much for debugging/experimenting with web pages.

If iOS Safari had the inspector/debugger, or just inspector with live JS console, I would almost never need to use my laptop (which is just Chromebook, but runs full Chrome).