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I’m guessing that React is keeping track of the current component instance that is executing when the hook is called, instead of JavaScript keeping track of wha
by baddox 8y ago
I’m guessing that React is keeping track of the current component instance that is executing when the hook is called, instead of JavaScript keeping track of what ‘this’ is bound to when ‘this.setState’ is called. One could say that both systems are “magic,” but it looks like the React team considers the behavior of ‘this’ in JavaScript to be a source of confusion for React developers.
- acemarke 8y agoYes, yes, and yes. You can see the current implementation in react-dom@16.7.0-alpha.0 - see https://unpkg.com/react-dom@16.7.0-alpha.0/cjs/react-dom.development.js https://unpkg.com/react-dom@16.7.0-alpha.0/cjs/react-dom.dev... for the actual code. Do a search for some of the effect names, like `useLayoutEffect()`, to see the implementation details. React already knows which specific component it's rendering, regardless of whether it's a class component instance, or a specific function component. Looks like what it's ultimately doing is just tracking some additional metadata added to React's internal bookkeeping - search for instances of things like `workInProgressHook.memoizedState`. And as someone who spends a large portion of my time answering questions from new React devs, I can confirm that the behavior of `this` in classes is an _endless_ source of confusion. Mitigating that is going to be a big improvement long-term.