Solid retry logic with rxjs5

retry.js

// emits a value after `init` ms, then after `init * exp` ms, then `init * exp * exp` ms, etc.
function expInterval(init, exp) {
  return Observable.create((observer) => {
    let n = init;
    let id;

    function next() {
      observer.next(n);
      n *= exp;
      id = setTimeout(next, n);
    }

    id = setTimeout(next, n);

    return () => {
      clearTimeout(id);
    };
  });
}

// Sends a request and retries when the browser sends a `online` event,
// as well as after 1sec, 2sec, 4sec, 8sec, etc...
function solidRetryLogic(request) {
  return Observable.ajax(request)
    .retryWhen(() => Observable.merge(
      Observable.fromEvent(window, 'online'),
      expInterval(1000, 2),
    ));
}