laravel/php/bootstrap -- js tech!

Hey.

Looking at a bunch of online sites regarding laravel/bootstrap. A key part
of the webapp process is the decision on which js tech is implemented.

I've seen a bunch of github/open source code that has react/vue. I'm
wondering, how difficult/easy is it to "change" functions/logic in an app
using one of the js tech to another?

Ie, if I found a chunk of frontside logic/code using 'react', that I want
to copy/cut/paste and use in an app that uses 'vue', what kind of pain am I
going to be dealing with!

thanks