problem description

5c. .. ,.() 

the environmental background of the problems and what methods you have tried

 10.3ios5c
,  babel-polyfill,es6-promise,

related codes

/ / Please paste the code text below (do not replace the code with pictures)

main.js
    import "babel-polyfill"
    import Es6Promise from "es6-promise"
    require("es6-promise").polyfill()
    Es6Promise.polyfill()
webpack.base.conf.js
    entry: {
        app: ["babel-polyfill","./src/main.js"]
    }

what result do you expect? What is the error message actually seen?

1. SyntaxError: Cannot declare a let variable twice: "t".   vendor.js 
2. TypeError: undefined is not an object (evaluating "r[n].call")

? 

.babelrc 
    {
      "presets": [
        ["env", {
          "modules": false,
          "targets": {
            "browsers": ["> 1%", "last 2 versions", "not ie <= 8"]
          }
        }],
        "stage-2"
      ],
      "plugins": ["transform-vue-jsx", "transform-runtime"],
      "env": {
        "test": {
          "presets": ["env", "stage-2"],
          "plugins": ["istanbul"]
        }
      }
    }

webpack.base.conf.js
    "use strict"
    const path = require("path")
    const utils = require("./utils")
    const config = require("../config")
    const vueLoaderConfig = require("./vue-loader.conf")
    function resolve (dir) {
      return path.join(__dirname, "..", dir)
    }
    
    module.exports = {
      context: path.resolve(__dirname, "../"),
      entry: {
        app: ["./src/main.js"]
      },
      output: {
        path: config.build.assetsRoot,
        filename: "[name].js",
        publicPath: process.env.NODE_ENV === "production"
          ? config.build.assetsPublicPath
          : config.dev.assetsPublicPath
      },
      plugins: [
        new webpack.ProvidePlugin({
          $: "jquery",
          jQuery: "jquery",
          "windows.jQuery": "jquery"
        })
      ],
      resolve: {
        extensions: [".js", ".vue", ".json"],
        alias: {
          "vue$": "vue/dist/vue.esm.js",
          "@": resolve("src"),
        }
      },
      module: {
        rules: [
          {
            test: /\.vue$/,
            loader: "vue-loader",
            options: vueLoaderConfig
          },
          {
            test: /\.js$/,
            loader: "babel-loader",
            include: [resolve("src"), resolve("test"), resolve("node_modules/webpack-dev-server/client")]
          },
          {
            test: /\.(png|jpe?g|gif|svg)(\?.*)?$/,
            loader: "url-loader",
            options: {
              limit: 10000,
              name: utils.assetsPath("img/[name].[hash:7].[ext]")
            }
          },
          {
            test: /\.(mp4|webm|ogg|mp3|wav|flac|aac)(\?.*)?$/,
            loader: "url-loader",
            options: {
              limit: 10000,
              name: utils.assetsPath("media/[name].[hash:7].[ext]")
            }
          },
          {
            test: /\.(woff2?|eot|ttf|otf)(\?.*)?$/,
            loader: "url-loader",
            options: {
              limit: 10000,
              name: utils.assetsPath("fonts/[name].[hash:7].[ext]")
            }
          }
        ]
      },
      node: {
        // prevent webpack from injecting useless setImmediate polyfill because Vue
        // source contains it (although only uses it if it"s native).
        setImmediate: false,
        // prevent webpack from injecting mocks to Node native modules
        // that does not make sense for the client
        dgram: "empty",
        fs: "empty",
        net: "empty",
        tls: "empty",
        child_process: "empty"
      }
    }