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网道教程：promise

40＋ 大厂常考 JS 手写题系列【摸鱼必备】（不该用 push，见测试）

Promise.allSettled

Promise.allSettled - 图1

  1. Promise.myAllSettled = promiseArr => {
  2.     return new Promise((resolve, reject) => {
  3.         if (!promiseArr[Symbol.iterator]) {
  4.             throw new TypeError(`${promiseArr} is not iterable`);
  5.         }
  7.         if (!Array.isArray(promiseArr)) {
  8.             promiseArr = Array.from(promiseArr);
  9.         }
  11.         const resArr = [];
  12.         let count = 0;
  14.         promiseArr.forEach((element, index) => {
  15.             Promise.resolve(element).then(
  16.                 valule => {
  17.                     resArr[index] = {
  18.                         status: 'fulfilled',
  19.                         valule
  20.                     }
  21.                     count++;
  23.                     if (count === promiseArr.length) resolve(resArr);
  24.                 },
  25.                 reason => {
  26.                     resArr[index] = {
  27.                         status: 'rejected',
  28.                         reason
  29.                     }
  30.                     count++;
  32.                     if (count === promiseArr.length) resolve(resArr);
  33.                 }
  34.             );
  35.         });
  36.     })
  37. };

测试

iterator 相关测试案例见这里

注意 setTimeout 设定的时间与输出数组的顺序。

  1. const p1 = new Promise((resolve, reject) => {
  2.     setTimeout(resolve, 1000, 'p1');
  3. });
  5. const p2 = new Promise((resolve, reject) => {
  6.     setTimeout(reject, 500, 'p2');
  7. });
  9. const p3 = new Promise((resolve, reject) => {
  10.     setTimeout(reject, 1500, 'p3');
  11. }).catch(e => e);
  13. Promise.myAllSettled([p1, p2, p3])
  14.     .then(res => console.log(res));
  16. Promise.allSettled([p1, p2, p3])
  17.     .then(res => console.log(res));
  19. // [
  20. //   {status: 'fulfilled', value: 'p1'},
  21. //   {status: 'rejected', reason: 'p2'},
  22. //   {status: 'fulfilled', value: 'p3'}
  23. // ]