Deep link to a native app from a browser, with a fallback

deep-link-from-browser.js

function DeepLinker(options) {
  if (!options) {
    throw new Error('no options')
  }

  var hasFocus = true;
  var didHide = false;

  // window is blurred when dialogs are shown
  function onBlur() {
    hasFocus = false;
  };

  // document is hidden when native app is shown or browser is backgrounded
  function onVisibilityChange(e) {
    if (e.target.visibilityState === 'hidden') {
      didHide = true;
    }
  };

  // window is focused when dialogs are hidden, or browser comes into view
  function onFocus() {
    if (didHide) {
      if (options.onReturn) {
        options.onReturn();
      }

      didHide = false; // reset
    } else {
      // ignore duplicate focus event when returning from native app on
      // iOS Safari 13.3+
      if (!hasFocus && options.onFallback) {
        // wait for app switch transition to fully complete - only then is
        // 'visibilitychange' fired
        setTimeout(function() {
          // if browser was not hidden, the deep link failed
          if (!didHide) {
            options.onFallback();
          }
        }, 1000);
      }
    }

    hasFocus = true;
  };

  // add/remove event listeners
  // `mode` can be "add" or "remove"
  function bindEvents(mode) {
    [
      [window, 'blur', onBlur],
      [document, 'visibilitychange', onVisibilityChange],
      [window, 'focus', onFocus],
    ].forEach(function(conf) {
      conf[0][mode + 'EventListener'](conf[1], conf[2]);
    });
  }

  // add event listeners
  bindEvents('add');

  // expose public API
  this.destroy = bindEvents.bind(null, 'remove');
  this.openURL = function(url) {
    // it can take a while for the dialog to appear
    var dialogTimeout = 500;

    setTimeout(function() {
      if (hasFocus && options.onIgnored) {
        options.onIgnored();
      }
    }, dialogTimeout);

    window.location = url;
  };
}

/* usage */

var url = 'fb://profile/240995729348595';
var badURL = 'lksadjgajsdhfaskd://slkdfs';

var linker = new DeepLinker({
  onIgnored: function() {
    console.log('browser failed to respond to the deep link');
  },
  onFallback: function() {
    console.log('dialog hidden or user returned to tab');
  },
  onReturn: function() {
    console.log('user returned to the page from the native app');
  },
});

linker.openURL(url);

@spaschold yes, universal links are a much better solution - I wrote this library to support a legacy app, in our newer app we use universal links exclusively.

In my case using IOS in safari, when app is already installed. It redirects to the native app (which is good) but then again redirect it to appstore as well (onIgnored called). I am frustrated on how to get rid of this. This is really a good solution but again there is no difference if we use simple redirect line of app link and setTimeOut and redirect to store only instead of this fancy onFocus and visibility events etc things.

If anyone has solution for this? @diachedelic

Are you able to discover why onVisibilityChange is not being called after the native app opens, @vatsal-gadhiya-searce? Perhaps dialogTimeout needs to be increased? What version of iOS are you using?

@diachedelic Thanks for your response, I am using IOS 14.4.2(iPhone XR) and safari 14.4.2. But i am sure, it is not related to IOS version. As i have already tested in many versions. It's the same behaviour. It's not consistence actually. sometimes it works sometimes it doesn't.

Also as you said about onVisibilityChange is not being called right, but i guess it's about onBlur as you are changing hasFocus to false onBlur and checking it in onIgnored. correct me if i am wrong.

Just FYI: I have not written any code of redirection inside onFallback and onReturn. it's onIgnored only where i have appstore redirection.

Code usage:

 var url = 'noq://home';
  var appURL = 'https://apps.apple.com/gb/app/noq/id1515913853'
  var linker = new DeepLinker({
    onIgnored: function() {
      window.location = appURL;
      console.log('browser failed to respond to the deep link');
    },
    onFallback: function() {
       console.log('dialog hidden or user returned to tab');
    },
    onReturn: function() {
      console.log('user returned to the page from the native app');
    },
  });
  linker.openURL(url);

Steps to reproduce:
If the app is not installed it calls onIgnored and redirect to Appstore (which is fine). Install the app from Appstore, Again open the same or other link, it redirects to the native app(which is fine) but again take me back to Appstore (which is weird) and I debug and found that onIgnored has been called even it redirects me to native app.

It would be life saver! if we get the solution for this @diachedelic

I am happy to debug as per your suggestion.

Install the app from Appstore, Again open the same or other link, it redirects to the native app

@vatsal-gadhiya-searce, does a dialog appear at this point, asking if you would like to open the native app? That is the expected behaviour.

@diachedelic Yup, The dialog appears like "Open this in NOQ"? click ok redirects to the native app and then again redirect back to browser opening Appstore.

One thing i observed, if i close all the tabs of safari and open the link it works. it doesn't redirect back to the browser after native redirection when the app already installed.

@vatsal-gadhiya-searce, can you please increase dialogTimeout to 5000 and check if onBlur is called when that dialog is shown?

@diachedelic, increased dialogTimeout to 5000. onBlur is called but it is still inconsistent. sometimes called sometimes it doesn't.

@vatsal-gadhiya-searce Ahh that's a shame. I'm afraid I can't help you if that's the case :(

So Universal links only :) No solution.

Hello, is it possible to hide the alert "Safari cannot open the page because the address is invalid"?
Or we have to use Universal links for this?
Thank you

It is not possible "check" whether the browser can handle a certain type of deep link for security reasons, sorry @biandtlp.

Hey @diachedelic, very nice writeup. Do you happen to know if there's a way to open to Safari via deeplink? I tested using this URL for google chrome: googlechrome://www.google.com and it works nicely but I wonder if there's the same thing for Safari.

Hey @luizcieslak, I didn't know you could do that with Chrome! Sorry but I don't know about Safari.

I'm not the type to leave comments. Thank you so much. God bless you

Thank you king

working on iOS 17.0.3, had to tweak the timeout values a bit but otherwise works beautifully, ty.
behaviour in safari is if user does not have the app installed, onFallback is triggered.
in chrome, onIgnored is triggered. onReturn fires as expected in both browsers

try this.

function openDeepLink(url: string, options?: Partial<{ onOpen?: () => void; onFail?: () => void; waitTime?: number }>) {
  let timeout: NodeJS.Timeout;
  let interval: NodeJS.Timer;
  let visible: DocumentVisibilityState = 'visible';

   const handleOpen = () => {
      window.removeEventListener('visibilitychange', () => true);
      options?.onOpen?.();
  };
  const handleResponse = () => {
    if (visible === 'visible') return options?.onFail?.();
    clearInterval(interval);
    handleOpen();
  };

  try {
    window.addEventListener('visibilitychange', (e) => (visible = (e.target as Document)?.visibilityState));
    timeout = setTimeout(handleResponse, options?.waitTime || 5000);

    interval = setInterval(() => {
      if (visible === 'hidden') {
        clearTimeout(timeout);
        handleResponse();
      }
    }, options?.waitTime || 5000);

    window.location.href = url;
  } catch (error) {
    options?.onFail?.();
  }
}

openDeepLink("fb://profile/100004452732850", {onOpen: console.log, onFail: console.error});

Tested on last version of Firefox 124, Android 13. Not working because even if a dialog appears to redirect to the app, the pages doesn't loose focus.

Can it be fixed?