icecream-declarative.js

import { from, zip } from 'rxjs';
import { scan } from 'rxjs/operators';

const iceCreamFlavors = ['vanilla', 'chocolate', 'strawberry'];
const iceCreamPrices = ['$5.50', '$5.75', '$6.00'];

const iceCreamFlavorToPrice$ = zip(
  from(iceCreamFlavors),
  from(iceCreamPrices),
).pipe(scan((prev, [flavor, price]) => {
  return {
    ...prev,
    [flavor]: price
  };
}, {}));