mergeAll
Example 1: mergeAll with promises
// RxJS v6+
import { map, mergeAll } from 'rxjs/operators';
import { of } from 'rxjs';
const myPromise = val =>
new Promise(resolve => setTimeout(() => resolve(`Result: ${val}`), 2000));
//emit 1,2,3
const source = of(1, 2, 3);
const example = source.pipe(
//map each value to promise
map(val => myPromise(val)),
//emit result from source
mergeAll()
);
/*
output:
"Result: 1"
"Result: 2"
"Result: 3"
*/
const subscribe = example.subscribe(val => console.log(val));
Example 2: mergeAll with concurrent parameter
// RxJS v6+
import { take, map, delay, mergeAll } from 'rxjs/operators';
import { interval } from 'rxjs';
const source = interval(500).pipe(take(5));
/*
interval is emitting a value every 0.5s. This value is then being mapped to interval that
is delayed for 1.0s. The mergeAll operator takes an optional argument that determines how
many inner observables to subscribe to at a time. The rest of the observables are stored
in a backlog waiting to be subscribe.
*/
const example = source
.pipe(
map(val => source.pipe(delay(1000), take(3))),
mergeAll(2)
)
.subscribe(val => console.log(val));
/*
The subscription is completed once the operator emits all values.
*/
- 🎥 💵 - André Staltz
Last modified 1yr ago