JS中Promise.all 与 Promise.race的区别小结

  function PromiseAll(arr) {
    const promises = Array.from(arr);
    const result = [];
    return new Promise((resolve, rejected) => {
      for (let i = 0; i < promises.length; i++) {
        promises[i]
          .then((res) => {
            result[i] = res;
            if (result.length === promises.length) {
              resolve(result);
            }
          })
          .catch((err) => {
            rejected(err);
          });
      }
    });
  }
  const promise1 = new Promise((resolve, reject) => {
    setTimeout(() => {
      resolve(1000);
    }, 1000);
  });
  const promise2 = new Promise((resolve, reject) => {
    setTimeout(() => {
      resolve(200);
    }, 200);
  });
  const promise3 = new Promise((resolve, reject) => {
    setTimeout(() => {
      reject(300);
    }, 300);
  });

  PromiseAll([promise1, promise2, promise3])
    .then(function (values) {
      console.log('全部成功', values);
    })
    .catch((values) => {
      console.log('有一个失败', values);
    });

  function PromiseRace(arr) {
    const promises = Array.from(arr);
    return new Promise((resolve, reject) => {
      try {
        for (let i = 0; i < promises.length; i++) {
          Promise.resolve(promises[i]).then(
            // 第一个成功的结果，直接resolve新Promise
            (value) => resolve(value),
            // 第一个失败的原因，直接reject新Promise
            (reason) => reject(reason)
          );
        }
      } catch (error) {
        // 参数校验/遍历出错时，直接reject新Promise
        reject(error);
      }
    });
  }
  const p1 = new Promise((resolve, reject) => {
    setTimeout(() => {
      reject(100);
    }, 100);
  });
  const p2 = new Promise((resolve) => {
    setTimeout(() => {
      resolve(500);
    }, 5000);
  });
  const p3 = new Promise((resolve) => {
    setTimeout(() => {
      resolve(1000);
    }, 1000);
  });
  PromiseRace([p1, p2, p3])
    .then((res) => console.log(`第一个成功状态：${res}`, 'success'))
    .catch((err) => console.log(`第一个失败状态：${err}`, 'error'));