How to solve: Custom Promise.all Implementation?

Question

Accepted Answer

To implement `Promise.all`:
1. Return a new `Promise`. If the input array is empty, resolve immediately with an empty array.
2. Initialize a `results` array and a `completedCount` counter.
3. Iterate over the promises using `forEach`. For each item, resolve it using `Promise.resolve(p)`.
4. Store the resolved value in the `results` array at the corresponding index (preserving order). Increment `completedCount`.
5. If `completedCount === promises.length`, resolve the outer promise.
6. If any promise throws or rejects, reject the outer promise immediately.