使用 Promise 实现请求自动重试
"use strict";
/**
*
* @author xgqfrms
* @license MIT
* @copyright xgqfrms
* @created 2020-11-20
* @modified
*
* @description
* @description
* @difficulty Easy Medium Hard
* @complexity O(n)
* @time O(n)
* @augments
* @example
* @link
* @solutions
*
* @best_solutions
*
*/
const log = console.log;
const autoRefetch = (url = ``, times = 3) => {
const promise = fetch(url);
promise.then(res => res.json(), err => {
if(times > 0) {
times -= 1;
promise = fetch(url);
}
}).catch(err => {
return Promise.reject(err);
})
return promise;
}
function maxRequest(url = ``, times = 3) {
return new Promise((resolve, reject) => {
if (times === 0) {
reject('max request number')
return
}
Promise.resolve(fetch(url)).then(value => {
log(`OK`)
resolve(value);
}).catch(() => {
log(`Error`)
times -= 1;
return maxRequest(url, times)
})
})
}
// function maxRequest(fn, maxNum) {
// return new Promise((resolve, reject) => {
// if (maxNum === 0) {
// reject('max request number')
// return
// }
// Promise.resolve(fn()).then(value => {
// resolve(value)
// }).catch(() => {
// return maxRequest(fn, maxNum - 1)
// })
// })
// }
模拟 Promise.all & Promise.allSettled
Promise.all
要么全部 promise 结果都成功了，返回全部的 promise 构成的一个结果值的数组；
要么只要有一个 promise 失败了，就返回失败了的 promise 的 error 值，默认 undefined
一句话总结: 全部 promise 结果都成功了，返回一个有所有成功的结果值的数组; 只要有一个promise 失败了，就的返回失败结果;
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/all
PromiseAll = function(promises) {
const values = [];
let count = 0;
return new Promise((resolve, reject) => {
promises.forEach((promise, index) => {
// promise.then ? 强制转换
Promise.resolve(promise).then(res => {
count += 1;
values[index] = res;
if (count === promises.length) {
resolve(values);
}
}, err => {
reject(err);
})
})
})
}
```js
// pending...
> Promise.allSettled 返回全部的 promise 的结果，无论 promise 结果是成功还是失败，构成一个可迭代的数组对象
成功的 promise 返回一个有 status: 'fulfilled' 和 value 构成的对象
失败的 promise 返回一个有 status: 'rejected' 和 reason 构成的对象
一句话总结: 无论 promise 是成功了还是失败了, 最终都返回一个有 status 和 value 或 reason 构成的对象数组;
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/allSettled
```js
PromiseAllSellted = function(promises) {
const result = [];
let count = 0;
return new Promise((resolve, reject) => {
// promise.then ? 强制转换
promises.forEach((promise, index) => {
Promise.resolve(promise).then(res => {
result[index] = {
status: `fullfilled`,
value: res,
}
}, err => {
result[index] = {
status: `rejected`,
reason: err,
}
}).finally(() => {
count++
if (count === promises.length) {
resolve(result)
}
})
})
})
}
Promise.allSettled & Promise.all & Promise.race & Promise.any All In One
https://www.cnblogs.com/xgqfrms/p/13414614.html
refs
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