File _app.js per Nextjs com registrazione service worker

_app.js

import App, { Container } from 'next/app'

export default class MyApp extends App {
  static async getInitialProps({ Component, router, ctx }) {
    let pageProps = {}

    if (Component.getInitialProps) {
      pageProps = await Component.getInitialProps(ctx)
    }

    return { pageProps }
  }

  componentDidMount() {
    if ('serviceWorker' in navigator) {
      window.addEventListener('load', () => {
        navigator.serviceWorker.register('/service-worker.js').then(registration => {
          console.log('SW registered: ', registration);
        }).catch(registrationError => {
          console.log('SW registration failed: ', registrationError);
        });
      });
    }
  }
  
  render () {
    const { Component, pageProps } = this.props

    return (
      <Container>
          <Component {...pageProps} />
      </Container>
    )
  }
}