composeAsync

1/**
2 * Composes asynchronous functions from right to left.
3 *
4 * @param fns - Functions to compose (right to left).
5 * @returns A function that applies the composed functions to an input.
6 */
7export function composeAsync<T>(
8  ...fns: Array<(input: any) => Promise<any> | any>
9): (input: T) => Promise<any> {
10  return async (input: T): Promise<any> => {
11    let result = input;
12    for (let i = fns.length - 1; i >= 0; i--) {
13      result = await fns[i](result);
14    } 
15    return result;
16  };
17}

1test('composeAsync - composes two async functions', async () => {
2  const add = async (x: number) => x + 2;
3  const double = async (x: number) => x * 2;
4
5  const composed = composeAsync(add, double);
6  const result = await composed(3);
7
8  expect(result).toBe(8); // double(3) = 6; add(6) = 8
9});
10
11test('composeAsync - handles mixed sync and async functions', async () => {
12  const toStr = (x: number) => `Value: ${x}`;
13  const increment = async (x: number) => x + 1;
14
15  const composed = composeAsync(toStr, increment);
16  const result = await composed(4);
17
18  expect(result).toBe('Value: 5');
19});
20
21test('composeAsync - returns original value when no functions', async () => {
22  const composed = composeAsync();
23  const result = await composed('test');
24
25  expect(result).toBe('test');
26});