promiseAll.js

function isPromise(obj) {
  return (
    !!obj && (typeof obj === 'function' || typeof obj === 'object') && typeof obj.then == 'function'
  );
}

function isPromise(object) {
  return (
    !!object && (typeof obj === 'function' || typeof obj === 'object') && object instanceof Promise
  );
}
function PromiseAll(arr) {
  return new Promise((resolve, reject) => {
    const len = arr.length,
      result = [];
    let succeed = 0;
    for (let i = 0; i < len; ++i) {
      const cur = arr[i];
      if (isPromise(cur)) {
        arr[i].then((res) => {
          process(i, res);
        }, reject);
      } else {
        process(i, cur);
      }
    }
    function process(index, value) {
      result[index] = value;
      if (++succeed === len) {
        resolve(result);
      }
    }
  });
}

function myPromiseAll(arr) {
  let res = [];
  let containPromise = false;
  return new Promise((resolve, reject) => {
    for (let i = 0; i < arr.length; i++) {
      if (isPromise(arr[i])) {
        containPromise = true;
        arr[i]
          .then((data) => {
            res[i] = data;
            if (res.length === arr.length) {
              resolve(res);
            }
          })
          .catch((error) => {
            reject(error);
          });
      } else {
        res[i] = arr[i];
      }
    }
    if (!containPromise) resolve(res);
  });
}