This article is for beginners. https://react-projects.netlify.app/ When implementing using React on this site, when I did ** npm start **, I got an error as the title says.
When you translate the error sentence of the title, it looks like this ** "Don't try to install manually. The package manager will install it automatically. However, a different version of webpack was detected at the top of the tree. "** In other words, ** "webpack is installed more than once in the upper directory" **, right?
Certainly my app directory contained "node_module", so it seems to be duplicated there. However, even if I deleted ** node_module, it didn't change, so I went to the last resort. ** **
Suddenly I came to the conclusion, but I solved it by creating a ".env" file directly under the application directory and adding the following line.
.env
SKIP_PREFLIGHT_CHECK=true
By the way, the full text of the error statement is here I'm sorry it's long. .. ..
There might be a problem with the project dependency tree.
It is likely not a bug in Create React App, but something you need to fix locally.
The react-scripts package provided by Create React App requires a dependency:
"webpack": "4.44.2"
Don't try to install it manually: your package manager does it automatically.
However, a different version of webpack was detected higher up in the tree:
/Users/ishiwatahiroshishou/node_modules/webpack (version: 5.1.3)
Manually installing incompatible versions is known to cause hard-to-debug issues.
If you would prefer to ignore this check, add SKIP_PREFLIGHT_CHECK=true to an .env file in your project.
That will permanently disable this message but you might encounter other issues.
To fix the dependency tree, try following the steps below in the exact order:
1. Delete package-lock.json (not package.json!) and/or yarn.lock in your project folder.
2. Delete node_modules in your project folder.
3. Remove "webpack" from dependencies and/or devDependencies in the package.json file in your project folder.
4. Run npm install or yarn, depending on the package manager you use.
In most cases, this should be enough to fix the problem.
If this has not helped, there are a few other things you can try:
5. If you used npm, install yarn (http://yarnpkg.com/) and repeat the above steps with it instead.
This may help because npm has known issues with package hoisting which may get resolved in future versions.
6. Check if /Users/ishiwatahiroshishou/node_modules/webpack is outside your project directory.
For example, you might have accidentally installed something in your home folder.
7. Try running npm ls webpack in your project folder.
This will tell you which other package (apart from the expected react-scripts) installed webpack.
If nothing else helps, add SKIP_PREFLIGHT_CHECK=true to an .env file in your project.
That would permanently disable this preflight check in case you want to proceed anyway.
P.S. We know this message is long but please read the steps above :-) We hope you find them helpful!
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! [email protected] start: `react-scripts start`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the [email protected] start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
npm ERR! A complete log of this run can be found in:
npm ERR! /Users/ishiwatahiroshishou/.npm/_logs/2020-11-03T10_08_18_340Z-debug.log
I paid attention to this line in this error statement.
If nothing else helps, add SKIP_PREFLIGHT_CHECK=true to an .env file in your project.
Translated, "Add SKIP_PREFLIGHT_CHECK = true to your project's .env file if nothing else helps." So you can use this as a last resort ...
** Add this to npm start !! **
Compiled with warnings.
src/App.js
Line 1:17: 'useState' is defined but never used no-unused-vars
Line 2:8: 'SingleColor' is defined but never used no-unused-vars
Line 4:8: 'Values' is defined but never used no-unused-vars
src/SingleColor.js
Line 1:17: 'useState' is defined but never used no-unused-vars
Line 1:27: 'useEffect' is defined but never used no-unused-vars
Line 2:8: 'rgbToHex' is defined but never used no-unused-vars
src/utils.js
Line 3:21: Expected '===' and instead saw '==' eqeqeq
Search for the keywords to learn more about each warning.
To ignore, add // eslint-disable-next-line to the line before.
I was able to start! !! After that, you can check the startup by accessing localhost: 3000.
However, it doesn't make sense, so I'll try to deepen it in the future.
** Don't forget that it's a last resort! !! ** **