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);

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?