Inferno vs React

This document is out of date, React Fire is going to implement many of the Inferno speedups: https://github.com/facebook/react/issues/13525

Docs:

React components are functions that return virtual dom nodes aka React Components
components have lifecycle events managed by React instead of the browser
components have a synthetic event system that wraps browser events
VirtualDOM diffed against real DOM on every render

There are basically 3 layers that can each contribute to slowness:
- react components receiving new props/state
- react components running render() to produce a virtual dom node
- virtual dom node being rendered to the real DOM
Each layer gets 10x slower as you get closer to the DOM, so it's important to avoid rendering as early in the layers as possible, e.g. don't pass new props to a component if it doesn't need to re-render, or use shouldComponentUpdate to skip rendering when not needed
React doesn't inspect state/props contents deeply to decide whether to render, it just rerenders, that's why implementing a real shouldComponentUpdate is critical if you care about performance

"if React were re-written from scratch, this is how it would be done", inferno fixes many of the design pitfalls that led to React becoming slow

~8kb Inferno vs 45kb React (gzipped), much faster load and parse time
React can never make the fundamental, backwards-incompatible API changes needed to get to inferno speeds (mainly getting rid of synthetic events)
inferno-compat and API similarities mean switching back and forth is easy if needed
same development setup and browser tooling

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