npm 不会启动反应应用程序，需要依赖项：“webpack-dev-server”：“3.1.14”

Question

我正在尝试创建一个新的 react-app 并启动​​它，我之前已经创建了 react 应用程序，但没有错误，但是这次当我 npm start 时出现此错误

 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>

我已经在错误日志中详细尝试了所有步骤，但仍然无法正常工作，对导致此错误的原因有什么想法吗？ 提前致谢

Answer 1

似乎您想在本地项目中依赖 webpack-dev-server。 也许您需要在项目中运行npm install而不是~主目录？

从您的输出中，注意这些行。

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.

所以我会

cd ./my-project
npm i

Answer 2

你自己安装了 webpack-dev-server 吗？ 它似乎已由您或其他项目安装安装。 Webpack 适用于您的本地开发环境，因此另一个安装与您的项目足够接近，以干扰 react 尝试在您的项目文件夹中安装的副本。 错误消息中的步骤 1-4 应该可以解决您的问题。 如果您已经这样做了但仍然无法正常工作，那么您下次尝试安装 React 包时是否收到了不同的错误消息？

Answer 3

我遇到了同样的问题，这种方法对我有用。

请按照以下步骤操作：

1. 从桌面启动终端并编写以下命令：

    npm uninstall webpack-dev-server

   这将从您的节点模块全局卸载webpack-dev-server包。

2. 回到你项目的终端并安装webpack-dev-server包：

    npm install webpack-dev-server@version

   _{注意： version部分（以上）应该等于错误消息中要求的版本。}

    npm install webpack-dev-server

3. 现在启动 npm：

    npm start

当您使用npx create-react-app命令而不是npm create-react-app命令创建项目时，通常会发生此错误。