Example of a webpack configuration to get workers code transpiled. Hint: "Rule.enforce".

babel-loader-worker-loader.js

{
  test: /\.js$/,
  use: [
    {
      loader: 'babel-loader',
      options: {
        // Babel loader options
      },
    },
  ],
},
{
  test: /-worker\.js$/,
  enforce: 'post',
  use: [
    {
      loader: 'worker-loader',
      options: {
        // Worker loader options
      },
    },
  ],
},