RxJS: Simple If condition for Observables in TypeScript

ifCondition.ts

// Simple if condition that stops Observable from continuing passed condition function returns false.
// There's also an option to run else callback if needed.

/*
 * USAGE
 * 
 * of(events).pipe(
 *   ifCondition(event => event.name.endsWith('anything'), () => console.log('Not the anything event'))
 * )
 */

export function ifCondition<I>(condition: (...args) => boolean, elseCallback?: (I) => any) {
  return switchMap<I, Observable<I | never>>(value => {
    if (condition(value)) {
      return of(value);
    }
    if (elseCallback) {
      elseCallback(value);
    }
    return NEVER;
  });
}