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JavaScript中怎么處理并行請(qǐng)求,很多新手對(duì)此不是很清楚,為了幫助大家解決這個(gè)難題,下面小編將為大家詳細(xì)講解,有這方面需求的人可以來學(xué)習(xí)下,希望你能有所收獲。
1、使用Promise.all
const startTime = new Date().getTime() function request(time) { return new Promise(resolve => { setTimeout(() => { resolve(time) }, time) }) } let request1 = request(3000) let request2 = request(2000) Promise.all([request1, request2]).then(res => { console.log(res, new Date() - startTime) // [ 3000, 2000 ] 3001 })
2、自定義狀態(tài),在回調(diào)中判斷返回狀態(tài),待2個(gè)請(qǐng)求都有返回值時(shí)再做處理。
const startTime = new Date().getTime() function request(time) { return new Promise(resolve => { setTimeout(() => { resolve(time) }, time) }) } let state = [undefined, undefined] let request1 = request(3000) let request2 = request(2000) request1.then(res => { state[0] = res process() }) request2.then(res => { state[1] = res process() }) function process() { if (state[0] && state[1]) { console.log(state, new Date() - startTime) // [ 3000, 2000 ] 3001 } }
3、generator,yield
const startTime = new Date().getTime() function ajax(time, cb) { setTimeout(() => cb(time), time) } function request(time) { ajax(time, data => { it.next(data); }) } function* main() { let request1 = request(3000); let request2 = request(2000); let res1 = yield request1 let res2 = yield request2 console.log(res1, res2, new Date() - startTime) // 2000 3000 3001 } let it = main(); it.next();
4、有了generator,很容易想到async/await,畢竟async/await就是由generator實(shí)現(xiàn)的。
// setTimeout模擬異步請(qǐng)求,time為請(qǐng)求耗時(shí) const startTime = new Date().getTime() function request (time) { return new Promise(resolve => { setTimeout(() => { resolve(time) }, time) }) } (async function () { let request1 = request(3000) let request2 = request(2000) let res1 = await request1 console.log(res1, new Date() - startTime) // 3000 3001 let res2 = await request2 console.log(res2, new Date() - startTime) // 2000 3005 })()
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