koios.html

Add button (https)
<link rel="manifest" href="./manifest.webmanifest">
<button class="add-button">Add to home screen</button>
<style>
  .add-button {
  position: absolute;
  top: 1px;
  left: 1px;
}
</style>

<script>
if ('serviceWorker' in navigator) {
  window.addEventListener('load', function() {
    navigator.serviceWorker.register('/sw.js').then(function(registration) {
      // Registration was successful
      console.log('ServiceWorker registration successful with scope: ', registration.scope);
    }, function(err) {
      // registration failed :(
      console.log('ServiceWorker registration failed: ', err);
    });
  });
}
  
  
let deferredPrompt;
const addBtn = document.querySelector('.add-button');
   addBtn.style.display = 'none';
   console.log("start");
  window.addEventListener('beforeinstallprompt', (e) => {
    console.log("In beforeinstallprompt");
  // Prevent Chrome 67 and earlier from automatically showing the prompt
  e.preventDefault();
  // Stash the event so it can be triggered later.
  deferredPrompt = e;
  // Update UI to notify the user they can add to home screen
  addBtn.style.display = 'block';

  addBtn.addEventListener('click', (e) => {
    // hide our user interface that shows our A2HS button
    addBtn.style.display = 'none';
    // Show the prompt
    deferredPrompt.prompt();
    // Wait for the user to respond to the prompt
    deferredPrompt.userChoice.then((choiceResult) => {
        if (choiceResult.outcome === 'accepted') {
          console.log('User accepted the A2HS prompt');
        } else {
          console.log('User dismissed the A2HS prompt');
        }
        deferredPrompt = null;
      });
  });
});
  
  
</script>