What are the differences between observables and promises in JavaScript?

Question

So i\'ve read that observables are looking to overtake promises in terms of usage in some of upcoming JavaScript MVC\'s:

• Angular 2.0
• Falcor used by Ne

Answer 1

Promises are a representation of 1 future value. Observables are a representation for a possibly infinite amount of values.

Promises will trigger the fetching of that value immediately upon creation. Observables will only start producing values when you subscribe to them. (Unless it's a hot observable, but that's outside the scope of this question)

Promises are designed to represent AJAX calls. Observables are designed to represent anything: events, data from databases, data from ajax calls, (possibly infinite) sequences, etc.