Web / Typescript interview questions
What is the difference between Subject and BehaviorSubject?
A BehaviorSubject holds one value. When it is subscribed it emits the value immediately. A Subject doesn't hold value.
BehaviourSubject will return the initial value or the current value on Subscription.
var bSubject= new Rx.BehaviorSubject(0); // 0 is the initial value bSubject.subscribe({ next: (v) => console.log('observerA: ' + v) // output initial value, then new values on `next` triggers }); bSubject.next(1); // output new value 1 for 'observer A' bSubject.next(2); // output new value 2 for 'observer A', current value 2 for 'Observer B' on subscription bSubject.subscribe({ next: (v) => console.log('observerB: ' + v) // output current value 2, then new values on `next` triggers }); bSubject.next(3);
Subject does not return the current value on Subscription. It triggers only on .next(value) call and return/output the value.
var subject = new Rx.Subject(); subject.next(1); //Subjects will not output this value subject.subscribe({ next: (v) => console.log('observerA: ' + v) }); subject.subscribe({ next: (v) => console.log('observerB: ' + v) }); subject.next(2); subject.next(3);
More Related questions...
