CODE EXAMPLE FOR JAVASCRIPT

service worker

service worker is javascript file that run every time.It keeps running even you
close the browser.Due to this we can send push notification,offline mode.
//Register our service worker in index.html
<script>
  if('serviceWorker' in navigator){
  window.addEventListener('load', ()=> {
    //registering of serviceWorker.
  navigator.serviceWorker('./serviceworker.js')
  .then((reg)=> console.log("Success:", reg.scope));
  .catch((err)=> console.log("Failure: ", err));
  })}
 <script>
  
everything ok then we will see Sucess: localhost:3000 in console of browser