What are Hot Observables and Cold Observables?

  • Cold Observables are observables where data is produced inside the Observable. It can be treated as a unicast.
const obs$ = new Obserable((observer) => {
    observer.next(Math.random());
});
obs$.subscribe((data) => console.log(data)); // prints different value
obs$.subscribe((data) => console.log(data)); // prints different value
  • Hot Observables are observables where data is produced outside the Observable. It can be treated as a multicast.
const data = 5;
const obs$ = new Obserable((observer) => {
    observer.next(data);
});
obs$.subscribe((data) => console.log(data)); // prints 5
obs$.subscribe((data) => console.log(data)); // prints 5
  • Cold Observables are observables where data is produced inside the Observable. It can be treated as a unicast.
const obs$ = new Obserable((observer) => {
    observer.next(Math.random());
});
obs$.subscribe((data) => console.log(data)); // prints different value
obs$.subscribe((data) => console.log(data)); // prints different value
  • Hot Observables are observables where data is produced outside the Observable. It can be treated as a multicast.
const data = 5;
const obs$ = new Obserable((observer) => {
    observer.next(data);
});
obs$.subscribe((data) => console.log(data)); // prints 5
obs$.subscribe((data) => console.log(data)); // prints 5
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Sriram Mannava

I'm a full-stack developer and a software enthusiast who likes to play around with cloud and tech stack out of curiosity.

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