devServer: {

    port: 9878,

    open: true,

    overlay: {

      warnings: false,

      errors: true

    },

    proxy: {

      "/a_api": {

        target: "http://127.0.0.1:3003",

        changeOrigin: true, // 是否改变域名

        ws: true,

        pathRewrite: {

          // 路径重写

          "/a_api": "" // 这个意思就是以api开头的，定向到哪里, 如果你的后边还有路径的话， 会自动拼接上

        }

      }

    }

    // before: require('./mock/mock-server.js')

  }

 

另：.env.development 配置

# just a flag
ENV = 'development'

# base api
VUE_APP_BASE_API = '/a_api'

另：.env.production配置

# just a flag
ENV = 'production'

# base api
VUE_APP_BASE_API = '/a_api'