codesandbox / codesandbox/codesandbox-client
React useEffect run twice even strictMode is closed
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- Dominant language
- JavaScript
- Stars
- 13.6k
- Forks
- 2.4k
- Avg merge
- 6d 19h
- Merged PRs (30d)
- 2
Description
🐛 bug report
Preflight Checklist
- I have read the Contributing Guidelines for this project.
- I agree to follow the Code of Conduct that this project
adheres to. - I have searched the issue tracker for an issue that matches the one I want
to file, without success.
Description of the problem
The useEffect sometimes running twice
How has this issue affected you? What are you trying to accomplish?
To Reproduce
refresh the browser in sandbox several times, and you can see the console.log() run twice
Link to sandbox: link (optional)
https://codesandbox.io/p/devbox/black-hooks-znysly?file=%2Fsrc%2FApp.tsx%3A9%2C30
Your Environment
| Software | Name/Version |
|---|---|
| Сodesandbox | https://codesandbox.io/ |
| Browser | Chrome |
| Operating System | Macos |
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Begin with the linked CodeSandbox reproduction, specifically src/App.tsx around line 9,30, and refresh it repeatedly in Chrome with Strict Mode closed. Confirm whether console.log runs twice and use that behavior as the completion criterion; the issue does not name a repository file or test beyond the sandbox.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- javascript, react, typescript
- Domain
- frontend, web-dev
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100