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What is Observable?

AngularJunior~1 min read
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Observable is a data stream that you can observe (that is, subscribe to) and receive values from over time.

A real-life example:

Imagine a button. Every click is a new event. Observable is like a radio: it transmits signals, and you just listen.

In code:

ts
const stream$ = of(1, 2, 3); // stream of numbers stream$.subscribe(value => { console.log(value); // logs: 1, then 2, then 3 });
  • stream$ is the Observable
  • .subscribe() starts listening
  • inside it: what to do with each new value

Where it's used in Angular:

  • HttpClient.get(...) → returns an Observable
  • FormControl.valueChanges → the input stream
  • router.events → the router event stream

What Observables can do:

  • emit many values
  • work with asynchrony (requests, timers)
  • use operators (map, filter, switchMap, debounceTime)
  • complete or throw an error

Conclusion:

Observable is like a pipe that data flows through. You can stand next to it (subscribe) and react to every "drop". This is the foundation of reactivity in Angular and RxJS.

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