juniorReactive Programming
Observable vs Promise
Updated May 6, 2026
Short answer
Observables emit multiple values over time; Promises emit once.
Deep explanation
Observables are lazy, cancellable, and support streams. Promises are eager and resolve once. Observables support operators like map/filter.
Real-world example
Observables for UI events; Promises for API calls.
Common mistakes
- Assuming Observables always execute immediately.
Follow-up questions
- Can Observables replace Promises?
- Are Observables lazy?