npm 不會啟動反應應用程序，需要依賴項：“webpack-dev-server”：“3.1.14”

Question

我正在嘗試創建一個新的 react-app 並啟動​​它，我之前已經創建了 react 應用程序，但沒有錯誤，但是這次當我 npm start 時出現此錯誤

 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-dev-server": "3.1.14"

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

 C:\Users\ashraf\node_modules\webpack-dev-server (version: 3.1.9)

 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-dev-server" 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 C:\Users\ashraf\node_modules\webpack-dev-server is outside 
 your project directory.
 For example, you might have accidentally installed something in your home 
 folder.

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

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! learnreact@0.1.0 start: `react-scripts start`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the learnreact@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!     C:\Users\ashraf\AppData\Roaming\npm-cache\_logs\2019-02- 
04T20_36_39_924Z-debug.log
PS C:\Users\ashraf\Desktop\Files\LearnReact\learnreact>

我已經在錯誤日志中詳細嘗試了所有步驟，但仍然無法正常工作，對導致此錯誤的原因有什么想法嗎？ 提前致謝

Answer 1

似乎您想在本地項目中依賴 webpack-dev-server。 也許您需要在項目中運行npm install而不是~主目錄？

從您的輸出中，注意這些行。

However, a different version of webpack-dev-server was detected higher up 
 in the tree:

 C:\Users\ashraf\node_modules\webpack-dev-server (version: 3.1.9)
...

6. Check if C:\Users\ashraf\node_modules\webpack-dev-server is outside 
 your project directory.
 For example, you might have accidentally installed something in your home 
 folder.

所以我會

cd ./my-project
npm i

Answer 2

你自己安裝了 webpack-dev-server 嗎？ 它似乎已由您或其他項目安裝安裝。 Webpack 適用於您的本地開發環境，因此另一個安裝與您的項目足夠接近，以干擾 react 嘗試在您的項目文件夾中安裝的副本。 錯誤消息中的步驟 1-4 應該可以解決您的問題。 如果您已經這樣做了但仍然無法正常工作，那么您下次嘗試安裝 React 包時是否收到了不同的錯誤消息？

Answer 3

我遇到了同樣的問題，這種方法對我有用。

請按照以下步驟操作：

1. 從桌面啟動終端並編寫以下命令：

    npm uninstall webpack-dev-server

   這將從您的節點模塊全局卸載webpack-dev-server包。

2. 回到你項目的終端並安裝webpack-dev-server包：

    npm install webpack-dev-server@version

   _{注意： version部分（以上）應該等於錯誤消息中要求的版本。}

    npm install webpack-dev-server

3. 現在啟動 npm：

    npm start

當您使用npx create-react-app命令而不是npm create-react-app命令創建項目時，通常會發生此錯誤。