FindIndex method

aFindIndex.ts

// Signature of the callback
type CallBackFindIndex<T> = (
  value: T,
  index?: number,
  collection?: T[]
) => Promise<boolean>;

/**
 * Async FindIndex function
 *
 * @export
 * @template T
 * @param {T[]} elements
 * @param {CallBackFind<T>} cb
 * @returns {Promise<number>}
 */
async function aFindIndex<T>( elements: T[], cb: CallBackFindIndex<T> ): Promise<number> {
  for (const [index, element] of elements.entries()) {
    if (await cb(element, index, elements)) {
      return index;
    }
  }

  return -1;
}

// You can use as follows
const array = [1, 2, 3, 4];

const output = await aFindIndex<number>(array, async (i) => {
 return Promise.resolve(i === 2);
});