SCRIPT1002: Syntax error in IE11 with React + Babel + Webpack

Question

I'm trying to get my React App with ES2015 functionalities running in IE >= 11 using Webpack + Babel. The setup is custom, using the inferno-compat layer, so no create-react-app used here.

However - despite applying the latest babel-polyfill and babel-preset-env practices to my .babelrc and webpack config, I still get a SCRIPT1002: Syntax error within my bundle.js when trying to access the app with IE11.

When I follow the syntax error reference in IEs console, this is the part within the generated bundle.js that's conflicting (the arrow-function in particular):

function add(x, y) {
  if (y === undefined) {
    return yHolder => add(x, yHolder);
  }

  return x + y;
}

These are the relevant dependencies within my package.json:

"dependencies": {
  "inferno-redux": "^3.10.1",
  "react": "^15.6.0",
  "react-dom": "^15.6.0",
  "react-ga": "^2.2.0",
  "react-swipeable": "^4.1.0",
  "redux": "^3.7.2",
  "redux-saga": "^0.16.0",
  "regenerator-runtime": "^0.11.0"
},
"devDependencies": {
  //... stuff

  "babel-cli": "^6.26.0",
  "babel-core": "^6.25.0",
  "babel-eslint": "^7.2.3",
  "babel-loader": "^7.1.1",
  "babel-plugin-inferno": "^3.2.0",
  "babel-plugin-module-resolver": "^2.7.1",
  "babel-plugin-transform-es2015-arrow-functions": "^6.22.0",
  "babel-plugin-transform-es2015-spread": "^6.22.0",
  "babel-plugin-transform-regenerator": "^6.26.0",
  "babel-plugin-transform-runtime": "^6.23.0",
  "babel-polyfill": "^6.26.0",
  "babel-preset-env": "^1.6.1",
  "babel-preset-es2015": "^6.24.1",
  "babel-preset-flow": "^6.23.0",
  "babel-preset-react": "^6.24.1",

  //... some more stuff

  "webpack": "^3.8.1",
  "webpack-bundle-analyzer": "^2.9.1",
  "webpack-dev-middleware": "^1.12.2",
  "webpack-dev-server": "^2.9.5",
  "webpack-manifest-plugin": "^1.3.2",
  "webpack-merge": "^4.1.1",
}

This is my .babelrc:

{
  "presets": 
    [
    "react", 
    "flow",
    "es2015",
    [
      "env", { 
        "modules": "commonjs",
        "targets": {
          "browsers": ["last 2 versions", "ie >= 11"]
        }
      }
    ]
  ]
}

I include the babel-polyfill within my webpack.base.config.js here:

// ... stuff
entry: {
  index: ['babel-polyfill', './index.js'],
},
// ... more stuff

Any ideas what's missing to get it running in IE11?

Answer 1

I found the issue. I'm using the module rambdax as one of my devDependencies, which contains source code written in ES6 syntax (not transpiled to ES5) - more specifically arrow-functions => that are directly included within my bundle.js. IE11 of course can't execute arrow-functions or any other ES6 syntax.

Unfortunately neither Babel nor Webpack (UglifyJS Plugin) will touch the source of imported node_modules when compiling the bundle.js, which means: Module source code that gets imported as ES6 will remain ES6 in your webpack bundle.js.

See https://github.com/facebookincubator/create-react-app/issues/1125 for more information on this topic.

I also already filed an issue regarding this problem within the ´rambdax´ repository. You can find out more about it there: https://github.com/selfrefactor/rambdax/issues/4

Answer 2

Not sure if it is still an issue.

With Webpack 4 I have done that

{
    test: /\.js$/,
    include: [
        // absolute path to module 
    ]
}

Included modules go through Babel hook.