reactjs / reactjs/react.dev

[Suggestion]: StrictMode confusion about ordering of the events

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Descrizione

Summary

This thread comes really close to avoid repeating this question again.
However I still have some doubts about the chain of the events in the strict mode.

I will quote the answer which provide the most valuable feedback.

"The mental model for this is that React really does unmount the component, but when re-mounting the component we restore the previously used state instead of starting fresh, the way Fast Refresh does, or some future features will."

But if that's the case why the order of the events(rendering, setting state, effects etc) is different while running in strict mode and outside of it?

Here are the concrete examples:

  1. https://codesandbox.io/p/sandbox/2z4wq2. This sandbox runs inside a strict mode and by inspecting the console we can see that the order of the events is like this
render
state setter
render
state setter
effect
clean up
effect

The second render and state setter are dimmed out according to the documentation and that's fine. So at least on the surface it appears that react is triggering render function (and state setter) 2 times before moving to the effects.

  1. https://codesandbox.io/p/sandbox/93zfkw. This sandbox runs outside of the strict mode and there is a button to toggle the mounting of the component. If the component is mounted, unmounted and mounted again the order of the events is like this.
render
state setter
effect
clean up
render
state setter
effect

This example has the mental model I have always worked with and which is clear, so I would waste too much time on it since that's how React also behaves on production.

The question is, if react is really performing mounting, unmounting and remounting while is the order different?

To be honest I haven't noticed that this difference is making my code harder to reason about while working with StrictMode.
I would like to know the details, if possible. What does this approach help React achieve that original one does not?

Page

https://react.dev/reference/react/StrictMode

Details

I think it would be helpful to update the page to explain why the behavior in StrictMode is different than simply running mounting, unmounting and mounting again.

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Direzione di ricerca

Inizia dalla pagina di riferimento di React StrictMode e confronta la spiegazione attuale con il thread dell’issue collegato e i due esempi CodeSandbox. Chiarisci perché l’ordine osservato di render, state, effetti e cleanup in StrictMode differisce da un ciclo separato di mount-unmount-remount, e aggiorna la pagina in modo che la spiegazione risponda a questa distinzione.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Valutazione

Stack tecnologico
javascript, react
Ambito
documentation
Tipo di issue
Documentazione
Difficoltà
4/5
Tempo stimato
3-5 giorni
Stato di attività
Ferma
Chiarezza
Abbastanza chiara
Idoneità per principianti
35/100

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