在webpack.prod.conf.js 

plugins:[ ] 中  添加

new UglifyJsPlugin({
      uglifyOptions: {
        compress: {
          warnings: false,
        // 打包后 log 就不会出现了
          drop_debugger: true,
          drop_console: true,
          pure_funcs: ['console.log']
        }
      },
      sourceMap: config.build.productionSourceMap,
      parallel: true
    })