babel编译时出现:Error: Cannot find module ‘@babel/core‘

babel编译时出现:Error: Cannot find module ‘@babel/core’

ERROR in ./src/index.js
Module build failed (from ./node_modules/_babel-loader@8.1.0@babel-loader/lib/index.js):
Error: Cannot find module '@babel/core'
Require stack:
- D:\work\HBuilderXWorkspace\react\01.webpack-base\node_modules\_babel-loader@8.1.0@babel-loader\lib\index.js
- D:\work\HBuilderXWorkspace\react\01.webpack-base\node_modules\loader-runner\lib\loadLoader.js
- D:\work\HBuilderXWorkspace\react\01.webpack-base\node_modules\loader-runner\lib\LoaderRunner.js
- D:\work\HBuilderXWorkspace\react\01.webpack-base\node_modules\webpack\lib\NormalModule.js
- D:\work\HBuilderXWorkspace\react\01.webpack-base\node_modules\webpack\lib\NormalModuleFactory.js
- D:\work\HBuilderXWorkspace\react\01.webpack-base\node_modules\webpack\lib\Compiler.js
- D:\work\HBuilderXWorkspace\react\01.webpack-base\node_modules\webpack\lib\webpack.js
- D:\work\HBuilderXWorkspace\react\01.webpack-base\node_modules\_webpack-dev-server@3.11.0@webpack-dev-server\bin\webpac
k-dev-server.js
 babel-loader@8 requires Babel 7.x (the package '@babel/core'). If you'd like to use Babel 6.x ('babel-core'), you shoul
d install 'babel-loader@7'.
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:966:15)
    at Function.Module._load (internal/modules/cjs/loader.js:842:27)
    at Module.require (internal/modules/cjs/loader.js:1026:19)
    at require (internal/modules/cjs/helpers.js:72:18)
    at Object.<anonymous> (D:\work\HBuilderXWorkspace\react\01.webpack-base\node_modules\_babel-loader@8.1.0@babel-loade
r\lib\index.js:10:11)
    at Module._compile (internal/modules/cjs/loader.js:1138:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1158:10)
    at Module.load (internal/modules/cjs/loader.js:986:32)
    at Function.Module._load (internal/modules/cjs/loader.js:879:14)
    at Module.require (internal/modules/cjs/loader.js:1026:19)

babel-loader@8 requires Babel 7.x (the package '@babel/core'). If you'd like to use Babel 6.x ('babel-core'), you shoul d install 'babel-loader@7'.
Emmmm…应该是版本问题，那就去package.json里面改版本号好了。

  "devDependencies": {
    "babel-core": "^6.26.3",
    "babel-loader": "^7.1.5",
  },

改完来，加载一下package.json的包，执行cnpm install或者npm install嗯，，

dependencies和devDependencies

1. 使用环境:
   dependencies:生产环境下所依赖的 npm 包集合；
   devDependencies:开发和测试环境下所依赖的 npm 包集合；

2. 单个包安装方式:
   dependencies:

   # 在与 package.json 同级目录下执行
   # —sava-prod 为默认安装模式
   # 安装以后会自动在 package.json 的 dependencies 下添加 
   npm install <package-name> [—sava-prod]
   

   devDependencies:

   # 在与 package.json 同级目录下执行
   # 安装以后会自动在 package.json 的 devDependencies 下添加 
   npm install <package-name> —sava-dev
   

3. 集成安装方式:
   dependencies:

   # 在与 package.json 同级目录下执行
   # 安装 dependencies 和 devDependencies 中的所有 npm 包
   npm install
   # 仅安装 dependencies 下的所有 npm 包
   npm install —production
   

   devDependencies:

   # 在与 package.json 同级目录下执行
   # 安装 dependencies 和 devDependencies 中的所有 npm 包
   npm install