1. Why Vue"s Webpack template does not use polyfill can also use ES6+ methods such as Object.assign on IE browsers. And there is no babel-polyfill in the package.json and related configuration of the template
2. can"t babel-loader automatically add relevant polyfill based on ES6 usage in my code? I feel that using my configuration is based on the polyfill added by browserlist
3. when I use Webpack4 myself, I need to use the ES6+ method correctly on my IE browser. You need to add a line import "babel-polyfill" to the entry file.

attach my webpack configuration:

"use strict";
const path = require("path");
module.exports = {
  mode: "development",
  entry: {
    index: path.join(__dirname, "./index.js"),
  },
  output: {
    filename: "[name].bundle.js",
  },
  devtool: "cheap-module-eval-source-map",
  devServer: {
    contentBase: path.resolve(__dirname, "./"),
    port: 8000,
  },
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        use: {
          loader: "babel-loader",
          options: {
            cacheDirectory: true,
            presets: [[ "env", {
              useBuiltIns: true,
            }]],
            plugins: [ "transform-runtime" ],
          },
        },
      },
    ],
  },
};