Promise.all realizations without Promise.all

promise_all.js

// Simple Promise.all realization

function promiseAll(promises) {
  try {
    let len = promises.length;
    let count = len;
    const results = new Array(len).fill(null);
    return new Promise((resolve, reject) => {
      promises.forEach((p, idx) => {
        p.then((res) => {
          results[idx] = res;
          count -= 1;
          if (count === 0) resolve(results);
        }).catch((e) => reject(e));
      });
    });
  } catch (e) {
    return new Error("Error: ", e);
  }
}

const p1 = Promise.resolve(1);
const p2 = Promise.resolve(2);
const p3 = Promise.resolve(3);
const perror = Promise.reject('error')
promiseAll([p1, p2, p3]).then((res) => console.log(res)).catch(e => console.log(e));; // [1,2,3]
promiseAll([p1, p2, perror]).then((res) => console.log(res)).catch(e => console.log(e)); // error