You'll have to excuse my ignorance as I just like to lightly follow the JS web dev community and am no way a JS expert, but what is the reasoning behind the React spin-offs? There's Inferno, Preact, ivi, and possibly more, but are all of these so different that they require their own repository? Is it out of the question to simply contribute to the other existing open source projects? I imagine there are some backwards compatible breaking changes but it feels a bit weird to have so many React-like spinoffs. Could anyone shed a light on this? I'm genuinely curious.

Note: I'm the author of Inferno and know the authors of Preact and Ivi well.

That's a great question and one I frequently get asked. The "current" React codebase is legacy in many ways, the React team are hard at work on React Fiber which is complete re-write of the entire codebase.

The legacy codebase isn't something we can actively make better (I've had my PRs merged though) without a huge rewrite. If we tried to make changes, it would break React for many people due to how coupled many things are.

A lot has changed in the last few years and the approach to virtual DOM has been one of them. Going forward, the React team are making big efforts to change this.

6DM

I haven't kept up with React like I should. When you say they're undergoing a re-write, is this going to be like Angular 1 vs Angular 2? I just took a quick look at their react fiber demo page [0], is it going to be opinionated react as redux based? That's the vibe I'm getting from this.

[0] http://reactbits.github.io/fiber/

btown

Fiber is simply a fully-backwards-compatible performance enhancement, though that does it a huge disservice. It's actually figuring out how to run different parts of a render() function in different clock ticks, essentially making renders asynchronous so that animations don't jitter or drop frames, and different parts of the render tree can be prioritized out of order. Unless you were doing weird stuff with low-level animations or React internals, user code won't need to change, but it will instantly become buttery smooth. See https://github.com/acdlite/react-fiber-architecture for how.

Now, the preference for stateless functional components that has been popularized for user code by Redux is certainly a trend, and a focus of performance attention. But that's nothing new.