reactjs / reactjs/react.dev

[Suggestion]: Section "Queueing a Series of State Updates": await in event handler cause immediate rerender

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type: documentation
Dominant language
JavaScript
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Description

Summary

The documentation says here: "React waits until all code in the event handlers has run before processing your state updates"

This not the case when using await inside the handler!

Example

const [myNumber, setMyNumber] = useState(0);

async function handleClick(){
    setMyNumber(i => i + 1);
    await delay(100);
    setMyNumber(i => i + 1);
}

function delay(ms) {
    return new Promise(resolve => {
        setTimeout(resolve, ms);
    });
}

This will rerender the component twice!

Page

https://react.dev/learn/queueing-a-series-of-state-updates

Details

I suggest it should be mentioned as caveat/pitfall that if you call await inside an event handler,
all changes made to states before that await will then be flushed and trigger a rerender immediately, not waiting
for the event handler to finish completely.

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Read the “Queueing a Series of State Updates” page linked in the issue and reproduce the provided async event-handler example to confirm the behavior. Update that page with a caveat explaining that state updates before an await can flush before the handler finishes; done means the example and batching guidance are accurate and clear.

Written by the indexing model from the issue text.

Assessment

Tech stack
javascript, react
Domain
documentation
Issue type
Documentation
Difficulty
1/5
Estimated time
Under an hour
Activity status
Stale
Clarity
Clearly specified
Newbie friendliness
55/100

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