Rxjs forkJoin map values from array dynamically

Question

Hi I've an array of Boolean observables and want to perform logical AND operation but as of now I'm passing static values a, b but I don't know how many values would be there inside totalKeys array.

import { forkJoin } from 'rxjs';

...
canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Observable<boolean> {
private totalKeys: Observable<Boolean>[] = [];
// some logic
  
return forkJoin(this.totalKeys).pipe(
    map(([a, b]) => a && b)
  );
};

How can I dynamically add elements to map array and use logical AND on those instead of passing static params to map operator.

You can use the reduce() operator to perform a logical AND operation on the elements of an array return forkJoin(this.totalKeys).pipe( map(values => values.reduce((acc, val) => acc && val)) ); — Nishanth
– Nishanth, Commented Dec 5, 2022 at 7:51

Matthieu Riegler · Accepted Answer · 2022-12-05 08:35:49Z

2

Use every :

which will look like following for you.

map(items => items.every(Boolean))

The way it works is following : every item is converted to a boolean and every will check that every item is true. this is semanticly equivalent to having && on every item.

edited Dec 5, 2022 at 8:35

answered Dec 5, 2022 at 7:52

Matthieu Riegler

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3 Comments

Mitul Panchal Over a year ago

Would be great if you can elaborate more on this, how would I perform AND operation on each value.

akotech Over a year ago

@MatthieuRiegler shouldn't it be map(items => items.every(Boolean))?

Matthieu Riegler Over a year ago

@akotech yes, you're right

Eddy Lin · Accepted Answer · 2022-12-05 09:14:12Z

1

RxJS

every operator

like this

merge(...totalKeys).pipe(every(identity))

edited Dec 5, 2022 at 9:14

answered Dec 5, 2022 at 9:03

Eddy Lin

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