https://www.freecodecamp.org/news/how-to-add-push-notifications-to-a-web-app-with-firebase-528a702e13e1/ ReactDOM . render ( < ThemeProvider theme = { theme } > { /* CssBaseline kickstart an elegant, consistent, and simple baseline to build upon. */ } < CssBaseline /> < AppContextProvider > < App /> </ AppContextProvider > </ ThemeProvider > , document . querySelector ( '#root' ) ) initializeFirebase () push-notification.ts import firebase from 'firebase' export const initializeFirebase = () => { if ( 'serviceWorker' in navigator ) { navigator . serviceWorker . register ( './firebase-messaging-sw.js' ) . then ( function ( registration ) { console . log ( 'Registration successful, scope is:' , registration . scope ) }) . catch ( function ( err ) { console . log ( 'Service worker registration failed, error:' , err ...