在命令行中使用命令 npm run dev运行从网上下载的一个vue项目时出现了以下报错：

npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! ruoyi@3.6.0 dev: `vue-cli-service serve`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the ruoyi@3.6.0 dev 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\Administrator\AppData\Roaming\npm-cache\_logs\2021-08-17T11_52_18_441Z-debug.log

这里报错的原因是因为    node_modules文件的缺失。

解决办法：

npm i

PS E:\dine\Dine_Backend\wxdine\RuoYi-Vue-master\ruoyi-ui> npm i
npm WARN deprecated runjs@4.4.2: This project has been renamed to 'tasksfile'. Install using 'npm install tasksfile' instead.
npm WARN deprecated babel-eslint@10.1.0: babel-eslint is now @babel/eslint-parser. This package will no longer receive updates.
npm WARN deprecated html-webpack-plugin@3.2.0: 3.x is no longer supported
npm WARN deprecated eslint-loader@2.2.1: This loader has been deprecated. Please use eslint-webpack-plugin
npm WARN deprecated microcli@1.3.3: This project has been renamed to @pawelgalazka/cli . Install using @pawelgalazka/cli instead
npm WARN deprecated @hapi/joi@15.1.1: joi is leaving the @hapi organization and moving back to 'joi' (https://github.com/sideway/joi/issues/2411)
npm WARN deprecated request@2.88.2: request has been deprecated, see https://github.com/request/request/issues/3142
npm WARN deprecated chokidar@2.1.8: Chokidar 2 will break on node v14+. Upgrade to chokidar 3 with 15x less dependencies.
npm WARN deprecated microargs@1.1.2: This project has been renamed to @pawelgalazka/cli-args. Install using @pawelgalazka/cli-args instead
npm WARN deprecated @hapi/bourne@1.3.2: This version has been deprecated and is no longer supported or maintained
npm WARN deprecated @hapi/hoek@8.5.1: This version has been deprecated and is no longer supported or maintained
npm WARN deprecated @hapi/address@2.1.4: Moved to 'npm install @sideway/address'
npm WARN deprecated @hapi/topo@3.1.6: This version has been deprecated and is no longer supported or maintained
npm WARN deprecated har-validator@5.1.5: this library is no longer supported
npm WARN deprecated fsevents@1.2.13: fsevents 1 will break on node v14+ and could be using insecure binaries. Upgrade to fsevents 2.
npm WARN deprecated querystring@0.2.0: The
npm WARN deprecated resolve-url@0.2.1: https://github.com/lydell/resolve-url#deprecated
npm WARN deprecated urix@0.1.0: Please see https://github.com/lydell/urix#deprecated
npm WARN sass-loader@10.1.0 requires a peer of node-sass@^4.0.0 || ^5.0.0 but none is installed. You must install peer dependencies yourself.
npm WARN sass-loader@10.1.0 requires a peer of fibers@>= 3.1.0 but none is installed. You must install peer dependencies yourself.
npm WARN eslint-loader@2.2.1 requires a peer of eslint@>=1.6.0 <7.0.0 but none is installed. You must install peer dependencies yourself.
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@1.2.13 (node_modules\watchpack-chokidar2\node_modules\fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.13: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@1.2.13 (node_modules\webpack-dev-server\node_modules\fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.13: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})

added 17 packages from 48 contributors in 12.823s

16 packages are looking for funding
  run `npm fund` for details

PS E:\dine\Dine_Backend\wxdine\RuoYi-Vue-master\ruoyi-ui> npm run dev

> ruoyi@3.6.0 dev E:\dine\Dine_Backend\wxdine\RuoYi-Vue-master\ruoyi-ui
> vue-cli-service serve

再次启动后发现已经存在vue-cli-service scrvice

npm run dev

同时启动成功。