Use this operator to transform messages coming through a source Observable. Transforming function gets a message as an argument and should return a value to be sent through resulting Observable.
import { new Observable, map } from '@hullo/core';​new Observable(observer => {observer.next(Math.round(Math.random() * 100));}).pipe(map(n => n * 2)).subscribe({next: v => { console.log(v, 'is an even number') }});