实现 Promise.all

Promise.all() 方法返回一个 promise，全部成功返回才返回一个数组结果，当有一个错误返回就直接返回错误结果

const t = new Promise((resolve, reject) => {
  setTimeout(() => {
    resolve("success");
    // reject("t");
  }, 1000);
});

const h = new Promise((resolve, reject) => {
  setTimeout(() => {
    resolve("success");
    // reject("h");
  }, 1000);
});

Promise.myAll = function (promises) {
  return new Promise((resolve, reject) => {
    if (!Array.isArray(promises)) return;
    const result = [];
    const len = promises.length;
    for (let i = 0; i < len; i++) {
      Promise.resolve(promises[i])
        .then((r) => {
          result[i] = r;
          if (i === promises.length - 1) {
            return resolve(result);
          }
        })
        .catch((e) => {
          reject(e);
        });
    }
  });
};

Promise.myAll([t, h])
  .then((r) => {
    console.log(r, "r");
  })
  .catch((e) => {
    console.log(e, "e");
  });

//['success', 'success'] 'r'