class CancelablePromise {
constructor() {
this.pendingPromise = null
this.reject = null
}
request(requestFn) {
if (this.pendingPromise) {
this.cancel('取消重复请求')
}
const promise = new Promise((_, reject) => (this.reject = reject))
this.pendingPromise = Promise.race([requestFn(), promise])
return this.pendingPromise
}
cancel(reason) {
this.reject(reason)
this.pendingPromise = null
}
}
function request(delay) {
return () =>
new Promise(resolve => {
setTimeout(() => {
resolve('最后赢家是我')
}, delay)
})
}
const cancelPromise = new CancelablePromise()
// 模拟频繁请求5次
for (let i = 0; i < 5; i++) {
cancelPromise
.request(request(10))
.then((res) => console.log(res)) // 最后一个 最后赢家是我
.catch((err) => console.error(err)); // 前四个 取消重复请求
}