gistfile1.js

$(function() {
  /* The JavaScript history API can be a pain.
   *
   * For example, if we navigate out to PayPal to
   * perform a payment, PayPal is now in the history
   * and all history.back() calls or back button
   * presses from then on might cause a back navigation
   * out of the app and back to paypal, confusing the
   * user with a PayPal error page.
   *
   * This work-around will track the current length of
   * the history while navigating through the app so if
   * the last history recorded for the app is not the
   * most recent history state we can jump back to it
   * instead of just doing a normal history.back().
   *
   * There is a limitation though, if the user further
   * navigates after returning from the external service,
   * the history tracking will be reset. So to avoid this
   * the page they come back to from should only have two
   * options, (1) redo the transaction, (2) cancel the
   * transaction.
   */
  window.popBackToApp = function() {
    var lastPosition = parseInt(sessionStorage['last-position']);

    if (lastPosition) {
      history.go(lastPosition - history.length - 1);
    } else {
      history.back();
    }
  };

  window.addEventListener('push', function() {
    sessionStorage['last-position'] = history.length;
  });

  window.addEventListener('popstate', function() {
    if (history.state !== null) {
      sessionStorage['last-position'] = history.length;
    }
  });
});