iOS and navigation mode detection script

index.html

<script>
  //...
  
  function showIosInstall() {
    let iosPrompt = document.querySelector(".ios-prompt");
    iosPrompt.style.display = "block";
    iosPrompt.addEventListener("click", () => {
      iosPrompt.style.display = "none";
    });
  }
  
  // Detects if device is on iOS
  const isIos = () => {
    const userAgent = window.navigator.userAgent.toLowerCase();
    return /iphone|ipad|ipod/.test( userAgent );
  }
  // Detects if device is in standalone mode
  const isInStandaloneMode = () => ('standalone' in window.navigator) && (window.navigator.standalone);
  // Checks if should display install popup notification:
  if (isIos() && !isInStandaloneMode()) {
    showIosInstall();
  }
</script>