Transpiling ES6 for IE11 with Babel

Question

I'm new to babel and trying to transpile my es6 code to work with IE11. But when I run the code in IE11 I get js errors about my forEach code. From what I've read I needed to add the preset @babel/preset-env . I added that to my config file so I'm not sure why it's not transpiling those forEach calls.

const path = require('path');

module.exports = {
    entry: {
        setupForm: "./Scripts/es6/setupForm.js",
        prelimForm: "./Scripts/es6/prelimForm.js"
    },
    output: {
        filename: '[name].js',
        path: path.resolve(__dirname, './Scripts/build'),
    },
    module: {
        rules: [{
            loader: 'babel-loader',
            test: /\.js$/,
            exclude: /node_modules/,
            query: {
                presets: ['@babel/preset-env']
            }
        }]
    }
}

I thought that perhaps I needed to additionally reference the babel polyfill.js as discussed here so I added it to my page, however, I'm getting the same error about Object doesn't support property or method 'forEach' .

Here is my package.json file.

{
  "name": "OurSite",
  "version": "1.0.0",
  "description": "",
  "main": "map_embed.js",
  "directories": {
    "doc": "docs"
  },
  "scripts": {
    "build": "webpack"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "@babel/core": "^7.4.5",
    "@babel/preset-env": "^7.4.5",
    "babel-core": "^6.26.3",
    "babel-loader": "^8.0.6",
    "babel-polyfill": "^6.26.0",
    "babel-preset-env": "^1.7.0",
    "webpack": "^4.32.2",
    "webpack-cli": "^3.3.2"
  },
  "babel": {
    "presets": [
      "env"
    ]
  },
  "dependencies": {}
}

Answer 1

As of Babel 7.4.0 @babel/polyfill has been deprecated in favour of core-js and regenerator packages.

https://babeljs.io/docs/en/babel-polyfill#docsNav

Either include in webpack

module.exports = {
  entry: {
    main: [
      'core-js/stable',
      'regenerator-runtime/runtime',
      'src/main.js'
    ]
  }
}

OR include in your js at the top

import 'core-js/stable';
import 'regenerator-runtime/runtime';

Answer 2

Here's what you should do:

• Install @babel/polyfill
• Include @babel/polyfill in your entry (If you have more than 1 entry, and you don't plan to have both on the same page, include the polyfill in both)
• Make sure all babel packages have the same major version, ie 7.xx (don't worry about babel-loader - that's actually a webpack package, not a babel package).

Webpack

module.exports = {
    ...
    entry: {
        setupForm: ["@babel/polyfill", "./Scripts/es6/setupForm.js"],
        prelimForm: ["@babel/polyfill", "./Scripts/es6/prelimForm.js"]
    },
    ...
}

package.json

{
  ...
  "devDependencies": {
    "@babel/core": "^7.4.5",
    "@babel/preset-env": "^7.4.5",
    "@babel/polyfill": "^7.4.4",
    "babel-loader": "^8.0.6",
    "webpack": "^4.32.2",
    "webpack-cli": "^3.3.2"
  },
  ...
}