Challenge 3 — Solution

Task: Write a generator function* idGenerator(prefix) that yields
strings like "prefix-1", "prefix-2", "prefix-3", incrementing
forever. Create two SEPARATE generators with different prefixes
("user" and "order") and call .next().value three times on each,
interleaved, to confirm they don't interfere with each other.

function* idGenerator(prefix) {
    let count = 1;
    while (true) {
        yield `${prefix}-${count}`;
        count++;
    }
}

const userIds = idGenerator("user");
const orderIds = idGenerator("order");

console.log(userIds.next().value);
console.log(orderIds.next().value);
console.log(userIds.next().value);
console.log(orderIds.next().value);
console.log(userIds.next().value);
console.log(orderIds.next().value);


Expected output:

user-1
order-1
user-2
order-2
user-3
order-3


Notes:
- userIds and orderIds are two completely separate generator
  instances, each created by its own call to idGenerator — each one
  has its own private count, the same independence demonstrated with
  closures in Intermediate Chapter 2's makeIdGenerator challenge.
- Interleaving the .next() calls between the two generators proves
  they don't share state — userIds reaching "user-2" has no effect
  on orderIds, which is still only at "order-1" at that point.
- Each generator's count variable persists between .next() calls
  purely because of how yield pauses and resumes the function,
  exactly as explained earlier in this chapter.