一个异步请求/操作 模拟代码如下
const request = (url) => new Promise((resolve, reject) => {
setTimeout(() => {
Math.random() > 0.8 ? resolve(url+' ok') : reject(url + ' fail')
}, 1000)
})
request('https://jirengu.com')
.then(data => console.log(data))
.catch(err => console.log(err))
要求：实现一个函数retry ，能对原函数进行封装，达到如下效果：如果如果请求失败，会自动重新发起请求，最多尝试n次。
const request = (url) => new Promise((resolve, reject) => {
setTimeout(() => {
Math.random() > 0.8 ? resolve(url+' ok') : reject(url + ' fail')
}, 1000)
})
function retry() {
...
}
let request4 = retry(request, 4)
request4('https://jirengu.com')
.then(data => console.log(data)) //只要成功1次，进入该逻辑
.catch(err => console.log(err)) //连续失败4次，进入该逻辑
实现
const retry = (fn, n=3) => (...args) => {
function run() {
return fn(...args).then(data => {
return Promise.resolve(data)
}).catch(error => {
n--
if(n <= 0) {
return Promise.reject(error)
} else {
return run()
}
})
}
return run()
}
完整测试代码
let i = 0
const request = (url) => new Promise((resolve, reject) => {
console.log(`第${++i}次执行`)
setTimeout(() => {
Math.random() > 0.8 ? resolve(url + ' ok') : reject(url + ' fail')
}, 1000)
})
const retry = (fn, n=3) => (...args) => {
function run() {
return fn(...args).then(data => {
return Promise.resolve(data)
}).catch(error => {
n--
if(n <= 0) {
return Promise.reject(error)
} else {
return run()
}
})
}
return run()
}
let request4 = retry(request, 4)
request4('https://jirengu.com')
.then(data => console.log(data))
.catch(error => console.log(error))
