Redirecting to iOS or Android Application from JavaScript

here is an example JavaScript code that demonstrates how to redirect to an iOS or Android application:

 // function to redirect to an iOS or Android application
function redirectToApp(appStoreUrl, androidScheme, androidAppId, fallbackUrl) {
  // check if user is on an iOS device
  var isIOS = /iPad|iPhone|iPod/.test(navigator.userAgent) && !window.MSStream;
  
  // check if user is on an Android device
  var isAndroid = navigator.userAgent.toLowerCase().indexOf("android") > -1;
  
  if (isIOS) {
    // redirect to iOS app using App Store URL
    window.location.href = appStoreUrl;
    
    // if iOS app is not installed, fallback to the specified URL
    setTimeout(function() {
      window.location.href = fallbackUrl;
    }, 500);
  } else if (isAndroid) {
    // redirect to Android app using URI scheme
    window.location.href = androidScheme;
    
    // if Android app is not installed, redirect to Play Store URL
    setTimeout(function() {
      window.location.href = 'https://play.google.com/store/apps/details?id=' + encodeURIComponent(androidAppId);
    }, 500);
  } else {
    // fallback to the specified URL for other devices
    window.location.href = fallbackUrl;
  }
}

// example usage
redirectToApp('https://itunes.apple.com/us/app/myapp/id123456789', 'myapp://', 'com.example.myapp', 'https://example.com');

In this example, we define a function redirectToApp that takes four parameters: appStoreUrl (the App Store URL for the iOS app), androidScheme (the URI scheme for the Android app), iOSAppId (the bundle ID for the iOS app), and fallbackUrl (the URL to fallback to if the app is not installed).

The function checks if the user is on an iOS or Android device, and then redirects to the appropriate app using either the App Store URL or the URI scheme. If the app is not installed, the function falls back to the specified URL.