js 手写promise.all
2022/6/14 23:20:48
本文主要是介绍js 手写promise.all,对大家解决编程问题具有一定的参考价值,需要的程序猿们随着小编来一起学习吧!
- 入参必须实现iterator接口,一般为数组
- 全部成功才算成功,有一个失败就失败, 如果成功,结果顺序和入参顺序保持一致
- 返回一个新的promise,
Promise._all = function (promises) { if (!promises instanceof Array) throw 'promises must be an array' const length = promises.length let count = 0 const ret = [] if (!length) return [] return new Promise((resolve,reject) => { for (let i = 0; i < promises.length; i++) { promises[i].then(v => { count++ ret[i] = v count === length && resolve(ret) }, r => { reject(r) }) } }) } const doAsyncTask = (fn, timeout) => setTimeout(() => fn(), timeout) const p1 = new Promise((resolve, reject) => doAsyncTask(()=>{reject(1)},2000)) const p2 = new Promise((resolve, reject) => doAsyncTask(()=>{resolve(2)},1000)) const p3 = new Promise((resolve, reject) => doAsyncTask(()=>{resolve(3)},3000)) const res = Promise._all([p1,p2,p3]) res.then(v=>console.log(v),r=>console.log(r)) console.log(res);
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