[trueadm]

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.

[btown]

Certain optimizations that Inferno can do, like avoiding prototype objects, are pretty closely tied to React's API. Are these bottlenecks, or could React (with Fiber and the planned 2017H1 optimizations [0]) eventually become comparable to Inferno's performance for all but the most complex applications?

[0] https://github.com/reactjs/core-notes/blob/master/2016-12/de...

[trueadm]

There's no reason why React can't learn from Inferno. In fact, I'm aware that they're using a lot of the internals of Inferno to improve React Fiber. I'm sure we'll see more on this in the future :)

[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.

[trueadm]

Unlike Angular 1 -> Angular 2, React Fiber will be fully backwards compatible with the current React.

[danabramov]

I probably wouldn't claim 100% compatibility but we're already passing ~95% of the tests, and intend to fix more. There will likely be a few minor differences but we also have 20 thousand components that need to "just work" so we're striving for as much compat as possible, and any changes would be very contained.

[abritinthebay]

You can think of it much more like putting a more advanced engine & drivetrain in a classic race car.

Practically speaking for an end user not a lot will change, but React will be faster, non-blocking, and have a whole new set of applications.