在create-react-app后React npm start不起作用 [英] React npm start doesn't work after create-react-app

问题描述

我正在学习React，而英语却很差。我已经有两个React项目，但是它们都不起作用:(我按照以下步骤操作，

I'm learning just React and my english is poor. I have already two react project but they don't work either :( I following this steps,

npx create-react-app my-app
cd my-app
npm start

npx create-react-app my-app cd my-app npm start

，但是它不起作用。我尝试清理缓存并再次安装npm，但没有成功。我该如何解决呢？

but it doesn't work. I try clean cache and npm install again but didn't succeed. how can i solve this?

> my-app@0.1.0 start /Users/edu/Documents/htdocs/my-app
> react-scripts start


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:

  "babel-loader": "8.0.5"

Don't try to install it manually: your package manager does it automatically.
However, a different version of babel-loader was detected higher up in the tree:

  /Users/edu/node_modules/babel-loader (version: 8.1.0) 

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 "babel-loader" 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/edu/node_modules/babel-loader is outside your project directory.
     For example, you might have accidentally installed something in your home folder.

  7. Try running npm ls babel-loader in your project folder.
     This will tell you which other package (apart from the expected react-scripts) installed babel-loader.

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! my-app@0.1.0 start: `react-scripts start`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the my-app@0.1.0 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/edu/.npm/_logs/2020-09-17T00_43_20_777Z-debug.log

推荐答案

在输出中查看建议编号6。

Take a look at suggestion number 6 in your output.

检查/ Users / edu / node / modules / babel-loader是否为在您的项目目录之外。
例如，您可能不小心在主文件夹中安装了某些东西。

Check if /Users/edu/node_modules/babel-loader is outside your project directory. For example, you might have accidentally installed something in your home folder.

听起来好像您不小心在其中安装了npm您的主文件夹（ / Users / edu / ）而不是您的项目文件夹，并且您的项目正在依赖此依赖项。

It sounds like at some point you accidentally did an npm install in your home folder (/Users/edu/) instead of your project folder, and your project is picking up on this dependency.

解决方法是从 / Users / edu / 中删除​​node_modules，package.json和package-lock.json，而这些内容并不需要存在。

The fix is to delete node_modules, package.json, and package-lock.json from /Users/edu/, those don't need to be there.

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