Understanding, creating and subscribing to observables in Angular

When version 2 of Angular came out, it introduced us to observables. The Observable isn’t an Angular specific feature, but a new standard for managing async data that will be included in the ES7 release. Angular uses observables extensively in the event system and the HTTP service. Getting your head around observables can be quite a thing, therefore i’m here to explain it the easy way.

Photo by Tommy Lisbin on Unsplash

Observables

Observables are lazy collections of multiple values over time.

yeah, right…well, actually it’s pretty easy:

1. Observables are lazy
   You could think of lazy observables as newsletters. For each subscriber a new newsletter is created. They are then only send to those people, and not to anyone else.
2. Observables can have multiple values over time
   Now if you keep that subscription to the newsletter open, you will get a new one every once and a while. The sender decides when you get it but all you have to do is just wait until it comes straight into your inbox.

If you come from the world of promises this is a key difference as promises always return only one value. Another thing is that observables are cancelable. If you don’t want your newsletter anymore, you unsubscribe…