CODEWITHSUNDEEP
rxjs5
Stepan Suvorov
Stepan Suvorov

Reputation: 26196

How could I create Cold Subject in RxJS?

By default RxJs Subject is "Hot", but is it possible to create "Cold" Subject to get all the values propagated from it from the beginning?

i.e.:

let s = new Subject();
s.next(1);
s.next(2);
s.subscribe(n => console.log(n)); //to get here 1 2 3
s.next(3);

Upvotes: 4

Views: 1265

Answers (2)

KwintenP
KwintenP

Reputation: 4775

You can use a ReplaySubject to do this. The one thing to keep in mind is that a ReplaySubject expects a number during creation to know how many values it should buffer. You cannot buffer all the elements.

const subject = new Rx.ReplaySubject(10);

subject.next("1");
subject.next("2");
subject.next("3");
subject.next("4");
subject.next("5");

subject.subscribe(
  (val) => console.log(val)
);    

subject.next("6");

// Logs out 
// 1
// 2
// 3
// 4
// 5
// 6

jsbin: http://jsbin.com/rocofa/edit?js,console

Upvotes: 3

Richard Szalay
Richard Szalay

Reputation: 84754

ReplaySubject behaves exactly as you describe. See the ReactiveX Subject docs for more details.

Upvotes: 1

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