random-app/src/index.js

const serviceWorkerFile = require('file-loader!./service-worker.js')

if ('serviceWorker' in navigator) {
  navigator.serviceWorker.getRegistrations()
    .then(regs => Promise.all(regs.map(reg => reg.unregister())))
    .then(() => navigator.serviceWorker.register(serviceWorkerFile))
  
  .then(function(registration) {
    console.log('Registration successful, scope is:', registration.scope);
  })
  .catch(function(error) {
    console.log('Service worker registration failed, error:', error);
  });
}

document.addEventListener('DOMContentLoaded', () => {
  document.body.innerHTML = `<h1>Webpack-Starter</h1>`
})