configuration has an unknown property 'postcss'

Invalid configuration object. Webpack has been initialised using a configuration object that does not match the API schema.
 - configuration has an unknown property 'postcss'. These properties are valid:
 

module: {
    rules: [
        {
            test: /\.js$/,
            loader: 'babel-loader',
            exclude:path.resolve(__dirname,'/node_modules'),
            include:path.resolve(__dirname,'/src'),
            options: {
                presets: ['env']
            }
        },
        {
            test: /\.css$/,
            loader:"style-loader!css-loader!postcss-loader"
        }
    ]
},
postcss:[
  require('autoprefixer')({
      browsers: ['last 5 versions']
  })
]

原因是版本更新。现在的新版本操作:

在webpack.config.js同级目录创建一个postcss.config.js

在postcss.config.js中输入

module.exports = {

  plugins: {

    'autoprefixer': {browsers: 'last 5 version'}

  }

}

另外附上慕课网视频网址：

https://www.imooc.com/video/14197