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KovbenyaAlexander opened this issue Dec 12, 2020 · 15 comments
Open

Cannot read property 'forEach' of undefined #10242

KovbenyaAlexander opened this issue Dec 12, 2020 · 15 comments

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@KovbenyaAlexander
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Hello
I created a project using npx create-react-app my-app. If i use npm start, compilation is successful, but the page is blank.
I have not made any changes to the project.
The console contains an error:

react-refresh-runtime.development.js:465 Uncaught TypeError: Cannot read property 'forEach' of undefined
    at Object.injectIntoGlobalHook (react-refresh-runtime.development.js:465)
    at Object../node_modules/@pmmmwh/react-refresh-webpack-plugin/client/ReactRefreshEntry.js (ReactRefreshEntry.js:8)
    at __webpack_require__ (bootstrap:856)
    at fn (bootstrap:150)
    at Object.1 (reportWebVitals.js:14)
    at __webpack_require__ (bootstrap:856)
    at checkDeferredModules (bootstrap:45)
    at Array.webpackJsonpCallback [as push] (bootstrap:32)
    at main.chunk.js:1

Screenshot:
2020-12-12 (2)

@yves-zhou
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Today, I found this problem.

@avihaymenahem
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avihaymenahem commented Dec 15, 2020

Same here, running from npx here causes the same issue (no modifications maded)

EDIT:
A workaround for now so you can keep on working:
Disable the React DEV TOOLS extension on Chrome.

The problem comes from the global Hook which initiated wrong (Missing renderers prop on the object, which needs to be initiated with new Map())

@KovbenyaAlexander
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@avihaymenahem lol, I installed this extension and now the project is working correctly. but only in a browser with the extension

@blockmood
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@KovbenyaAlexander Close the Browser react plugin。

@albiummid
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@avihaymenahem lol, I installed this extension and now the project is working correctly. but only in a browser with the extension

that also worked for me. XD

@arron-chen
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so did i,how to do?

@arron-chen
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disabled the browser devtools will be fine, but i need this devtools to debug?

@hechengxixi
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@arron-chen the same case with me. do you find better way to debug?

@KevinAdu
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Did this issue ever get solved?

@callisto1337
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the same case

@voidoperator
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i've been getting a similar error when clearing localStorage manually (which is set by a useEffect, the data stored is an object that i'm state managing with react's context API).

Uncaught TypeError: Cannot read properties of undefined (reading 'forEach')
    at setup (backendManager.js:656:17)
    at welcome (backendManager.js:640:3)

@jarrodmjack
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@voidoperator I am getting this exact same issue with localstorage but cannot find a fix

@Shaker-Hamdi
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I'm not even using "Create React App" and I'm getting the same issue with "Vite" and "Next.js".
I think it's a "React Dev Tool" issue.

@idilTugba
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  • disable React Dev Tools plugin and refresh the localhost.
  • enable React Dev Tools
    everything working correctly now

@thany
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thany commented Jun 7, 2024

I'm getting this error without the react devtools as well. All I have to do is access my website running om localhost, through BrowserStack. Not sure what is happening, but it should be easy to reproduce with any CRA.

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