How to use babel/corejs3/webpack correctly for IE11?

Question

With my current config (see below), I'm getting this error:

   [object Error]{description: "Argument ob...", message: "Argument ob...", name: "TypeError", number: -2147418113, stack: "TypeError: ...", Symbol()_7.bs7gi3oa3wi: undefined}

I tried to dig based on Symbol()_ ... : undefined} but I couldn't find any clear indication.

This is my .babel.config.js:

module.exports = function (api) {
    api.cache(true);
    const presets = [
      [
        '@babel/preset-env',
        {
         // modules: false,
          corejs:"3.6.4",
          useBuiltIns: 'usage',
          targets: {
            browsers: [
              "edge >= 16",
              "safari >= 9",
              "firefox >= 57",
              "ie >= 11",
              "ios >= 9",
              "chrome >= 49"
            ]
          }
        }
      ]
    ];
    const plugins= [
        ["@babel/plugin-proposal-decorators", { decoratorsBeforeExport: true }],
        ["@babel/plugin-proposal-class-properties", { "loose": true }]
    ];
    return {
      presets,
      plugins
    }
  }

This is my webpackconfig.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.js$/,
       // exclude: /node_modules/,
       exclude : [
        /\bcore-js\b/,
        /\bwebpack\/buildin\b/
      ],
        use: {
          loader: 'babel-loader',
          options:{
            sourceType: "unambiguous"
          }
        },
      },
    ],
  },
  devtool:"cheap-source-map",
  resolve: {
    extensions: ['*', '.js'],
  },
  output: {
    path: path.resolve(__dirname, './dist'),
    filename: 'shim.js',
  }
};

I've also tried many alternatives, this is my current one, with entry:"usage" and not excluding node_modules.

This is from my package.json:

 "devDependencies": {
    "@babel/core": "^7.9.0",
    "@babel/plugin-proposal-class-properties": "^7.8.3",
    "@babel/plugin-proposal-decorators": "^7.8.3",
    "@babel/preset-env": "^7.9.5",
    "babel-loader": "^8.1.0",
    "eslint": "^6.8.0",
    "eslint-config-google": "^0.14.0",
    "webpack": "^4.42.1",
    "webpack-cli": "^3.3.11",
    "webpack-dev-server": "^3.10.3",
    "dotenv-webpack": "^1.7.0"
  },
  "dependencies": {
    "core-js": "^3.6.4",
    "ismobilejs": "^1.0.3",
    "localforage": "1.7.3",
    "postmate": "^1.5.2",
    "uuid": "^7.0.3"
  }

Error seems to come from the first invocation of the Postmate library i.e. new Postmate({...}) (I have a console.log just before). Prior to this call, I have one to localforage and the promise complete succesfully.

Answer 1

Using useBuiltIns: "usage"

---

You'll have to normally import the modules you want to use (i.g. Postmate) inside your code entry file; no polyfills; every polyfill used will be handled accordingly by @babel/preset-env. Also, the version of corejs in @babel/preset-env has to be a single number (i.e. 3 or 2).

Contents of babel.config.js:

module.exports = function (api) {
  api.cache(true);
  const presets = [
    [
      '@babel/preset-env',
      {
        corejs : {
          version : "3",
          proposals : true
        },
        useBuiltIns: 'usage',
        targets: {
          browsers: [
            "edge >= 16",
            "safari >= 9",
            "firefox >= 57",
            "ie >= 11",
            "ios >= 9",
            "chrome >= 49"
          ]
        }
      }
    ]
  ];
  const plugins= [
      ["@babel/plugin-proposal-decorators", { decoratorsBeforeExport: true }],
      ["@babel/plugin-proposal-class-properties", { "loose": true }]
  ];
  return {
    presets,
    plugins
  }
}

Contents of webpackconfig.js:

const path = require('path');

module.exports = {
  module: {
    rules: [
      {
        test: /\.(js|jsx)$/,
        exclude: [
          /\bcore-js\b/,
          /\bwebpack\/buildin\b/
        ],
        use: {
          loader: 'babel-loader',
          options: {
            babelrc: false,
            configFile: path.resolve(__dirname, 'babel.config.js'),
            compact: false,
            cacheDirectory: true,
            sourceMaps: false,
          },
        },
      },
    ],
  },
  devtool: "cheap-source-map",
  output: {
    path: path.resolve(__dirname, './dist'),
    filename: 'shim.js',
  }
}

Contents of entry JS file src/index.js:

import Postmate from 'postmate';

// Postmate and rest of the code
...

It will generate:

dist/shim.js      177K
dist/shim.js.map  140K

You can test an online distributed example working using useBuiltIns: "usage" in IE 11 here: https://zikro.gr/dbg/so/61044894/usage/. (The child iFrame has a button that changes parent window background color to a random color)

You can find a repository with the whole project and the usage example branch in this Github repository/branch: https://github.com/clytras/ie11-postmate/tree/usage

Using useBuiltIns: "entry"

---

According to this issue disqussion "using Symbol causes exception in IE11", you have to:

1. Exclude @babel-runtime and core-js in the rule for .js files.
2. Have corejs: "3" and useBuiltIns: 'entry' to @babel/preset-env preset inside babel.config.js file.
3. There have to be core-js/stable and postmate imports inside your entry source JS file.

Contents of babel.config.js:

module.exports = function (api) {
  api.cache(true);
  const presets = [
    [
      '@babel/preset-env',
      {
        corejs:"3",
        useBuiltIns: 'entry',
        targets: {
          browsers: [
            "edge >= 16",
            "safari >= 9",
            "firefox >= 57",
            "ie >= 11",
            "ios >= 9",
            "chrome >= 49"
          ]
        }
      }
    ]
  ];
  const plugins= [
      ["@babel/plugin-proposal-decorators", { decoratorsBeforeExport: true }],
      ["@babel/plugin-proposal-class-properties", { "loose": true }]
  ];
  return {
    presets,
    plugins
  }
}

Contents of webpackconfig.js:

const path = require('path');

module.exports = {
  module: {
    rules: [
      {
        test: /\.(js|jsx)$/,
        exclude: /@babel(?:\/|\\{1,2})runtime|core-js/,
        use: {
          loader: 'babel-loader',
          options: {
            babelrc: false,
            configFile: path.resolve(__dirname, 'babel.config.js'),
            compact: false,
            cacheDirectory: true,
            sourceMaps: false,
          },
        },
      },
    ],
  },
  devtool:"cheap-source-map",
  output: {
    path: path.resolve(__dirname, './dist'),
    filename: 'shim.js',
  }
}

Contents of entry JS file src/index.js:

import 'core-js/stable';
window.Postmate = require('postmate/build/postmate.min.js');

// Postmate and rest of the code
...

It will generate:

dist/shim.js      641K
dist/shim.js.map  459K

You can test in IE 11 here: https://zikro.gr/dbg/so/61044894/.

Answer 2

You're probably missing some imports, I'd suggest looking at what react-app-polyfills imports under the hood for IE11 support - the error message relates to Symbol. core-js>=3 no longer imports everything that IE11 needs with core-js/stable. At the time of this writing this might suffice:

// If  you need `fetch` or `Object.assign`
npm install whatwg-fetch object-assign

// Make sure we're in a Browser-like environment before importing polyfills
// This prevents `fetch()` from being imported in a Node test environment
if (typeof window !== 'undefined') {
  // fetch() polyfill for making API calls.
  require('whatwg-fetch');
}

// Object.assign() is commonly used with React.
// It will use the native implementation if it's present and isn't buggy.
Object.assign = require('object-assign');

/// This may rid you of your error message

// Support for...of (a commonly used syntax feature that requires Symbols)
require('core-js/features/symbol');
// Support iterable spread (...Set, ...Map)
require('core-js/features/array/from');

Hope this helps