> can they come back and build new React projects without significant re-training?
Absolutely. For one, React introduced a few primary concepts: components, JSX, and the component lifecycle. Whether you wrote functional components, class components, or moved to the new hooks-based components, these lifecycles are behaving the same. The way you write the lifecycle hook might be slightly different in a hooks world but it still exists the same. JSX is almost entirely unchanged in my experience. Composability and other techniques to pass data or context thru to the children still work the same as ever. Accessing DOM nodes still works the same as previously but with a new method as well.
In general, "the old way works but there's a new way too" sums up a lot of the core features. The library has updated and refined itself, but maintained back-compat with almost all old ways of using it, and conceptually stayed true.
Absolutely. For one, React introduced a few primary concepts: components, JSX, and the component lifecycle. Whether you wrote functional components, class components, or moved to the new hooks-based components, these lifecycles are behaving the same. The way you write the lifecycle hook might be slightly different in a hooks world but it still exists the same. JSX is almost entirely unchanged in my experience. Composability and other techniques to pass data or context thru to the children still work the same as ever. Accessing DOM nodes still works the same as previously but with a new method as well.
In general, "the old way works but there's a new way too" sums up a lot of the core features. The library has updated and refined itself, but maintained back-compat with almost all old ways of using it, and conceptually stayed true.