In this tutorial, we will learn about the Replay Subject of RXJS.

Replay Subject

ReplySubject stores multiple old Emittedvalue according to the specified time

For example we can store the last 3 value for the last 3 min we can do that 

import { ReplaySubject} from 'rxjs';

mySubject = new ReplaySubject<string>(3, 5000);

this.mySubject .next(1);
this.mySubject .next(2);
this.mySubject .next(3);
this.mySubject .next(4);


mySubject.subscribe(res => {
  console.log('1st sub:', res);
});

setTimeout(() => {
mySubject.subscribe(res => {
  console.log('2nd sub:', res);
});

},1000)

Above will give output: 

1st sub: 1
1st sub: 2
1st sub: 3
1st sub: 4
2nd sub: 3
2nd sub: 4

The Above example will store the last three emissions for 5 seconds as we are subscribing seconds subscriber after one second it will show the last two values