Babel not transpiling arrow functions (Webpack)

Question

When running webpack, and babel, the resulting bundle.js still contains arrow functions. This gives me a Syntax Error when running in Internet Explorer 10. I would like babel to replace the arrow functions with normal functions that IE can run.

My package.json has the following devDependencies:

"devDependencies": {
  "babel-cli": "^6.26.0",
  "babel-core": "^6.26.0",
  "babel-loader": "^7.1.4",
  "babel-preset-env": "^1.6.1",
  "babel-preset-es2015": "^6.24.1",
  "babel-preset-react": "^6.24.1",
  "babel-preset-stage-1": "^6.24.1",
  "css-loader": "^0.28.9",
  "imports-loader": "^0.7.1",
  "style-loader": "^0.19.1",
  "webpack": "^3.11.0",
  "webpack-dev-server": "^2.11.2"
}

My webpack.config.js looks like this:

module.exports = {
  entry: [
    'babel-polyfill',
    './src/index.js'
  ],
  output: {
    path: __dirname,
    publicPath: '/',
    filename: 'bundle.js'
  },
  module: {
    rules: [
    {
      test: /\.js$/,
      exclude: /node_modules/,
      loader: 'babel-loader'
    },
    {
      test: /\.css$/,
      use: ['style-loader', 'css-loader']
    }
    ],
  },
  resolve: {
    enforceExtension: false,
    extensions: ['.js', '.jsx']
  },
  devServer: {
    host: '0.0.0.0',
    port: 5000,
    historyApiFallback: true,
    contentBase: './'
  }
};

My .babelrc looks like this:

{ 
  "presets": 
  [
    ["env", { "targets": {"browsers": ["last 2 versions"]}, "debug": true }], 
    "react", 
    "stage-3"
  ]
}

To transpile, I run the command:

npm run build --production

And I get the following output in the console:

Using targets:
{
  "chrome": "62",
  "android": "4.4.3",
  "edge": "15",
  "firefox": "56",
  "ie": "10",
  "ios": "10.3",
  "safari": "10.1"
}

Modules transform: commonjs

Using plugins:
  check-es2015-constants {"android":"4.4.3","ie":"10"}
  transform-es2015-arrow-functions {"android":"4.4.3","ie":"10"}
  transform-es2015-block-scoped-functions {"android":"4.4.3","ie":"10"}
  transform-es2015-block-scoping {"android":"4.4.3","ie":"10"}
  transform-es2015-classes {"android":"4.4.3","ie":"10"}
  transform-es2015-computed-properties {"android":"4.4.3","ie":"10"}
  transform-es2015-destructuring {"android":"4.4.3","edge":"15","ie":"10"}
  transform-es2015-duplicate-keys {"android":"4.4.3","ie":"10"}
  transform-es2015-for-of {"android":"4.4.3","ie":"10"}
  transform-es2015-function-name {"android":"4.4.3","edge":"15","ie":"10"}
  transform-es2015-literals {"android":"4.4.3","ie":"10"}
  transform-es2015-object-super {"android":"4.4.3","ie":"10"}
  transform-es2015-parameters {"android":"4.4.3","ie":"10"}
  transform-es2015-shorthand-properties {"android":"4.4.3","ie":"10"}
  transform-es2015-spread {"android":"4.4.3","ie":"10"}
  transform-es2015-sticky-regex {"android":"4.4.3","ie":"10"}
  transform-es2015-template-literals {"android":"4.4.3","ie":"10"}
  transform-es2015-typeof-symbol {"android":"4.4.3","ie":"10"}
  transform-es2015-unicode-regex {"android":"4.4.3","ie":"10"}
  transform-regenerator {"android":"4.4.3","ie":"10"}
  transform-exponentiation-operator {"android":"4.4.3","ie":"10"}
  transform-async-to-generator {"android":"4.4.3","ie":"10"}
  syntax-trailing-function-commas {"android":"4.4.3","ie":"10"}

The transform-es2015-arrow-functions is listed as included, but when I open the generated bundle.js I can, for instance, see the following:

...

function encoderForArrayFormat(options) {
    switch (options.arrayFormat) {
        case 'index':
            return (key, value, index) => {
                return value === null ? [
                    encode(key, options),
...

The above makes use of an arrow function, and produces a syntax error in Internet Explorer. Other ES6 stuff like '...' gets transpiled.

What am I doing wrong?

Answer 1

I think an issue is related to query-string because it's written in ES6 and not transpiled to ES5. Try to downgrade version from 6 to 5.

yarn add query-string@5.1.1

Answer 2

it seems to be related to 'transform-es2015-function-name' plugin. see https://github.com/babel/babel/issues/4782#issuecomment-271367012 for details. So excluding the plugin should do the job.