It is pretty much the same, except there is no explicit loop and calls to wait for events written in JS/React code. Javascript itself runs a loop, instead of polling for events, you define events handlers, and DOM/React handles "redraw anything that needs it" part.
Just to be clear, the loop isn't explicit in a desktop toolkit either. You do not poll for events, and the toolkit handles the "redraw anything that needs it". So for example, in GTKmm (the C++ wrapper for GTK+), the event loop looks like:
Ah, it was quite a while since I looked at desktop GUI apps... It used to be just like OP described - you define logic, and then run pieces of it in the loop. It makes sense to abstract that away to standardize the process.
