mapSkipUndefined

Import

import { mapSkipUndefined } from 'ngxtension/map-skip-undefined';

Usage

You can use it as a normal map operator, but with the ability to skip some values: returning undefined (explicit or implicit).

import { from } from 'rxjs';
import { mapSkipUndefined } from 'ngxtension/map-skip-undefined';

const in$ = from([1, 42, 3]);
const out$ = in$.pipe(
  mapSkipUndefined((n) => {
    if (n % 2) return String(n * 2);
    //else return undefined // <-- this is the same as not returning anything!
    //In either case the even value is filtered out
  }),
); //infer Observable<string>

out$.subscribe(console.log); // logs: 2, 6

Bonus: filterUndefined

If you need to filter out undefined value from and Observable stream you can use the filterUndefined operator.

Example

import { filterUndefined } from 'ngxtension/map-skip-undefined';

const source$ = of(null, undefined, 42);
const filtered$ = source$.pipe(filterUndefined()); //emit only null and 42