<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8" /> <meta http-equiv="X-UA-Compatible" content="IE=edge" /> <meta name="viewport" content="width=device-width, initial-scale=1.0" /> <title>promise.all</title> </head> <body> <script> let link = `https://github.com/shfshanyue/Daily-Question/issues/500`; function pAll(_promises) { return new Promise((resolve, reject) => { // Iterable => Array const promises = Array.from(_promises); // 结果用一个数组维护 const r = []; const len = promises.length; let count = 0; for (let i = 0; i < len; i++) { // Promise.resolve 确保把所有数据都转化为 Promise Promise.resolve(promises[i]) .then(o => { // 因为 promise 是异步的，保持数组一一对应 r[i] = o; // 如果数组中所有 promise 都完成，则返回结果数组 if (++count === len) { resolve(r); } // 当发生异常时，直接 reject }) .catch(e => reject(e)); } }); } </script> <script> const sleep = seconds => new Promise(resolve => setTimeout(() => resolve(seconds), seconds)); </script> <script> function promiseAll(_promises) { return new Promise((resolve, reject) => { const promises = [..._promises]; const arr = []; let count = 1; for (let i = 0; i < promises.length; i++) { Promise.resolve(promises[i]).then( data => { arr[i] = data; if (++count === promises.length) { resolve(arr); } }, err => { reject(err); } ); } }); } </script> <script> function makeIterator(array) { let nextIndex = 0; return { next: function () { return nextIndex < array.length ? { value: array[nextIndex++], done: false } : { done: true }; } }; } let it = makeIterator(['哟', '呀']); console.log(it.next().value); // '哟' console.log(it.next().value); // '呀' console.log(it.next().done); // true </script> </body> </html>