[RxJS] Observables can complete

The Observer object has the functions next() and error(). In this lesson we will see the other (and last) function available on observers, complete(), and its purpose.

Completion is an important concept, as we will see later on. Imagine if you want to concatenate two observables. You can only do that if the first one ends. Then you know that the second observable takes over after that.

var bar = Rx.Observable.create(function (observer) {
  try {
    console.log('Hello');
    observer.next(42);
    observer.next(100);
    observer.next(200);
    setTimeout(function () {
      observer.next(300);
      observer.complete();
    }, 1000);
  } catch (err) {
    observer.error(err);
  }
});

bar.subscribe(
  function nextValueHandler(x) {
    console.log(x);
  },
  function errorHandler(err) {
    console.log('Something went wrong: ' + err);
  },
  function completeHandler() {
    console.log('done');
  }
);