function asyncFunc(e) {
  return new Promise((resolve, reject) => {
    setTimeout(() => resolve(e), e * 1000);
  });
}

const arr = [1, 2, 3];

function workMyCollection(arr, results = []) {
  return new Promise((resolve, reject) => {
    if (!arr.length) {
      return resolve(results);
    }

    const [element, ...rest] = arr;

    console.log(`element is ${element}`);

    asyncFunc(element)
    .then((result) => {
      results.push(result);

      if (!rest.length) {
        return resolve(results);
      }

      workMyCollection(rest, results)
        .then(resolve)
        .catch(console.error);
    });
  });
}

workMyCollection(arr, [])
  .then(result => console.log(`FINAL RESULT is ${result}`));