#422 Execute Promises in Series

Implement a function runInSeries that takes an array of functions, where each function returns a promise, and executes them one after another (in series).

The function should return a promise that resolves with an array of results, in the same order as the functions.

If any promise rejects, stop execution and reject immediately with that error.

Example

const tasks = [
  () => Promise.resolve(1),
  () => new Promise(res => setTimeout(() => res(2), 100)),
  () => Promise.resolve(3)
];

runInSeries(tasks).then(console.log);
// Output: [1, 2, 3]

const failingTasks = [
  () => Promise.resolve('a'),
  () => Promise.reject('error'),
  () => Promise.resolve('c')
];

runInSeries(failingTasks).catch(console.error);
// Output: error

Constraints

• Input is always an array of functions returning promises.
• Execution must be strictly sequential (no overlapping).
• Handle empty array input → should resolve to [].