Interview: reduce() cart price * qty

Compute the cart total, taking quantity into account.

1. Solve the task in the editor — no long theory.
2. Run the check and compare your output with the expected result.
3. Stuck? Open the solution and carry the approach into your own code.

const { from, reduce } = Rx;

const lines = [
  { price: 10, qty: 2 },
  { price: 5, qty: 1 },
];

const result$ = from(lines).pipe(
  reduce((sum, line) => sum + line.price * line.qty, 0)
);

result$.subscribe(value => console.log(value));