Webpack Uncaught ReferenceError: babelHelpers is not defined

Question

im developing a react application. For Routing i use react-router-dom and typesafe-react-router. My project is setup with webpack 4 and babel. To use the typesafe router i defined my routes.

routes.ts

import { route } from 'typesafe-react-router';

export enum RouteNames {
  HOME = 'HOME',
  ABOUT = 'ABOUT'
}

export const Routes = {
  [RouteNames.HOME]: route(''),
  [RouteNames.ABOUT]: route('about')
};

the routes are also used in other files like the App.tsx

    <div className="AppContainer">
      <Router>
        <h1>My React App</h1>
        <img src={logo} />
        <div className="NavLink">
          <Link to={Routes[RouteNames.HOME].create({})}>Home</Link>
          {' | '}
          <Link to={Routes[RouteNames.ABOUT].create({})}>About</Link>
        </div>

        <Switch>
          <Route
            path={Routes[RouteNames.HOME].template()}
            exact
            component={HomePage}
          />
          <Route
            path={Routes[RouteNames.ABOUT].template()}
            component={AboutPage}
          />
          <Route component={NotFoundPage} />
        </Switch>
      </Router>
    </div>

during the compilation everything is fine, but i get runtime errors:

routes.ts:8 Uncaught ReferenceError: babelHelpers is not defined
    at Module../src/pages/routes.ts (routes.ts:8)
    at __webpack_require__ (bootstrap:726)
    at fn (bootstrap:100)
    at Module../src/pages/index.ts (index.ts:1)
    at __webpack_require__ (bootstrap:726)
    at fn (bootstrap:100)
    at Module../src/app/App.tsx (App.tsx:1)
    at __webpack_require__ (bootstrap:726)
    at fn (bootstrap:100)
    at Module../src/bootstrap/index.tsx (index.tsx:1)

here is my.babelrc file:

{
  "presets": [
    "@babel/preset-env",
    "@babel/preset-react",
    "@babel/preset-typescript"
  ],
  "plugins": [
    "@babel/plugin-external-helpers",
    "@babel/plugin-proposal-class-properties",
    "@babel/plugin-proposal-object-rest-spread"
  ]
}

and here is my webpack.config.js

const path = require('path');
const { CheckerPlugin } = require('awesome-typescript-loader');
const HtmlWebpackPlugin = require('html-webpack-plugin');

module.exports = {
  entry: './src/bootstrap/index.tsx',
  devtool: 'source-map',
  resolve: {
    extensions: ['.ts', '.tsx', '.js', '.less']
  },
  output: {
    path: path.join(__dirname, '/dist'),
    filename: 'bundle.min.js'
  },
  module: {
    rules: [
      {
        test: /\.(js|jsx|tsx|ts)$/,
        exclude: /node_modules/,
        use: ['babel-loader']
      },
      {
        test: /\.css$/,
        use: ['style-loader', 'css-loader']
      },
      {
        test: /\.less$/,
        use: [
          {
            loader: 'style-loader'
          },
          {
            loader: 'css-loader'
          },
          {
            loader: 'less-loader',
            options: {
              javascriptEnabled: true
            }
          }
        ]
      },
      {
        test: /\.(png|jpg|gif|svg)$/i,
        use: [
          {
            loader: 'url-loader',
            options: {
              limit: 10000
            }
          }
        ]
      }
    ]
  },
  plugins: [
    new CheckerPlugin(),
    new HtmlWebpackPlugin({
      template: './src/bootstrap/index.html'
    })
  ]
};

i think mybee the issue is with the babel compiler having problems with the exported const enums. Is there a way to get this language feature of typescript working with babel?

Answer 1

Remove the @babel/plugin-external-helpers and use @babel/plugin-transform-runtime to load the helpers for you. The former plugin expects you to provide the helpers, which, for what I see, you're not.

Answer 2

It looks like you're using @babel/plugin-external-helpers . It'll prevent Babel from adding the required helper functions at the top of each file.

You can read more about the plugin in the Babel docs .

To solve your issue, I'd either replace the plugin with @babel/plugin-transform-runtime or install the required helpers manually.

Also, it is worth checking related issues on GitHub:

• https://github.com/babel/babel/issues/9366
• https://github.com/rollup/rollup/issues/2665