Open Facebook app on iOS if it exists, falling back to browser otherwise

open_facebook_app.js

function preventPopup(timeout) {
  clearTimeout(timeout);
  timeout = null;
  window.removeEventListener("pagehide", preventPopup);
}

function openFacebook(site, platform) {
  let fbAppUrl;
  switch (platform.type) {
    case "ios":
      fbAppUrl = `fb://page/?id=${site.thirdpartyId}`;
      break;
    case "android":
      // On android the facebook app seems to pick
      // up the fallback url instead of this one
      fbAppUrl = `fb://page/${site.thirdpartyId}`;
      break;
  }

  window.addEventListener("pagehide", preventPopup);
  document.addEventListener("pagehide", preventPopup);

  if (fbAppUrl) {
    console.log("opening fb app " + fbAppUrl);

    // try opening FB APP url in iframe so we don't show error dialogs
    // if the app isn't installed
    // var iframe = document.createElement("iframe");
    // document.body.appendChild(iframe);
    // iframe.setAttribute("style", "display:none;");
    // iframe.src = fbAppUrl;

    // 9/28/2020 - sneaking the app load in an iframe was no longer working
    // just open the app directly in this window so the user sees the
    //"are you sure" dialog on ios
    window.location = fbAppUrl;

    setTimeout(function () {
      //this fallback will catch if the app doesn't open
      window.location = site.url;
    }, 1000);
  } else {
    window.location = site.url;
  }
}