Promise

1、Promise.allSettled

  1. Promise.allSettled = Promise.allSettled || function (arr) {
  2.     let P = this;
  3.     return new P(function (resolve, reject) {
  4.         if (Object.prototype.toString.call(arr) !== '[object Array]') {
  5.             return reject(
  6.                 new TypeError(
  7.                     typeof arr +
  8.                     ' ' +
  9.                     arr +
  10.                     ' ' +
  11.                     ' is not iterable(cannot read property Symbol(Symbol.iterator))'
  12.                 )
  13.             );
  14.         }
  15.         let args = Array.prototype.slice.call(arr);
  16.         if (args.length === 0) return resolve([]);
  17.         let arrCount = args.length;
  18.         function resolvePromise(index, value) {
  19.             if (typeof value === 'object') {
  20.                 let then = value.then;
  21.                 if (typeof then === 'function') {
  22.                     then.call(
  23.                         value,
  24.                         function (val) {
  25.                             args[index] = { status: 'fulfilled', value: val };
  26.                             if (--arrCount === 0) {
  27.                                 resolve(args);
  28.                             }
  29.                         },
  30.                         function (e) {
  31.                             args[index] = { status: 'rejected', reason: e };
  32.                             if (--arrCount === 0) {
  33.                                 resolve(args);
  34.                             }
  35.                         }
  36.                     );
  37.                 }
  38.             }
  39.         }
  40.         for (let i = 0; i < args.length; i++) {
  41.             resolvePromise(i, args[i]);
  42.         }
  43.     });
  44. };