promise-vs-observable.md

What is the Difference Between Promises and Observables?

Promise

• Starts executing immediately once it is defined
• Can return only one value
• Not cancellable by default (need to combine with AbortController)
• Promise executes only onces (promise defined > then 1 > then 2);

Observable

• Won't start executing until we subscribe to it
• Can emit multiple streams of values
• Can be canceled by unsubscribing
• Observable executes every time we subscribe (observable defined > subscribe 1 > observable defined > subscribe 2)

References:

• https://blog.bitsrc.io/promises-vs-observables-674f4bc8ca5e