and-then.js

let pendingRequests = 0;

$(document)
  .ajaxStart(() => { pendingRequests += 1; })
  .ajaxStop(() => { pendingRequests -= 1; });

function andThen(callback) {
  wait().then(callback);
}

function wait() {
  return new RSVP.Promise(resolve => {
    const watcher = setInterval(() => {
      if (pendingRequests.length) { return; }
      clearInterval(watcher);
      resolve();
    }, 30);
  });
}