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forkJoin operator in RxJs

rxjs javascript typescript 218 words 2 minutes

forkJoin Operator

Can be imported from here:

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import { forkJoin } from 'rxjs';
// or
const { forkJoin } = require('rxjs');

For official documentation, visit https://rxjs-dev.firebaseapp.com/api/operators/endWith

Returns an observable that takes in input array of observables or dictionary of observables and emits last values before completion of observables (in array or dictionary object).

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import { forkJoin, of, timer } from 'rxjs';

const ob1$ = of(1, 2, 3, 4);
const ob2$ = Promise.resolve(8);
const ob3$ = timer(4000);
 
const result$ = forkJoin({
  foo: ob1$,
  bar: ob2$,
  baz: ob3$
});
result$.subscribe({
 next: value => console.log(value),
 complete: () => console.log('Completed!'),
});

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{foo: 4, bar: 8, baz: 0}
Completed!

Note: result is emitted after 4 seconds as timer(4000) takes 4 seconds to complete.

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import { forkJoin, of, timer } from 'rxjs';

const ob1$ = of(1, 2, 3, 4);
const ob2$ = Promise.resolve(8);
const ob3$ = timer(4000);
 
const result$ = forkJoin([ob1$, ob2$, ob3$]);
result$.subscribe({
 next: value => console.log(value),
 complete: () => console.log('Completed!'),
});

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[4, 8, 0]
Completed!

Note: result is emitted after 4 seconds as timer(4000) takes 4 seconds to complete.

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