Parallel Limit

Implement a parallelLimit(tasks, limit) function that runs an array of async task functions with a maximum concurrency of limit.

Requirements

• tasks is an array of functions, each returning a Promise<T>.
• At most limit tasks run simultaneously.
• Return a Promise<T[]> that resolves with results in the original order.
• If any task rejects, the returned promise rejects immediately.

Example

const delay = (ms, val) => () => new Promise(r => setTimeout(() => r(val), ms));
const results = await parallelLimit([
  delay(30, 'a'), delay(10, 'b'), delay(20, 'c')
], 2);
// results === ['a', 'b', 'c']