class PromisePool {
constructor(max, fn) {
this.max = max;
this.fn = fn;
this.pool = [];
this.urls = [];
}
start(urls) {
this.urls = urls;
while (this.pool.length < this.max) {
let url = this.urls.shift();
this.setTask(url);
}
let race = Promise.race(this.pool);
return this.run(race);
}
run(race) {
race
.then(res => {
let url = this.urls.shift();
this.setTask(url);
return this.run(Promise.race(this.pool));
})
}
setTask(url) {
if (!url) return
let task = this.fn(url);
this.pool.push(task);
console.log(`${url} 开始,当前并发数:${this.pool.length}`)
task.then(res => {
this.pool.splice(this.pool.indexOf(task), 1);
console.log(`${url} 结束,当前并发数:${this.pool.length}`);
})
}
}
const URLS = [
'bytedance.com',
'tencent.com',
'alibaba.com',
'microsoft.com',
'apple.com',
'hulu.com',
'amazon.com'
]
var requestFn = url => {
return new Promise(resolve => {
setTimeout(() => {
resolve(`任务${url}完成`)
}, 1000)
}).then(res => {
console.log('外部逻辑', res);
})
}
const pool = new PromisePool(5, requestFn);
pool.start(URLS)
console