promise线程池

// 异步请求，最大并发3，请求全部完成后打印结果
export async function asyncPool<T>(poolLimit: number, array: T[], iteratorFn: (item: T) => unknown) {
    let res: Promise<any>[] = [];
    let executing: Promise<any>[] = [];

    for (let item of array) {
        const p = Promise.resolve().then(() => iteratorFn(item));
        res.push(p);

        if (poolLimit <= array.length) {
            const e: Promise<any> = p.then(() => executing.splice(executing.indexOf(e), 1));
            executing.push(e);
            if (poolLimit <= executing.length) {
                await Promise.race(executing);
            }
        }
    }

    return Promise.all(res);
}

/**
 * 创建一个异步请求
 * @param i
 * @returns
 */
const curl = (i: number) => {
    console.log('开始' + i);
    return new Promise((resolve) =>
        setTimeout(
            () => {
                resolve(i);
                console.log('结束' + i);
            },
            1000 + Math.random() * 1000
        )
    );
};

// 创建一个数组
let urls = Array(10)
    .fill(0)
    .map((v, i) => i);

(async () => {
    const res = await asyncPool(3, urls, curl);
    console.log(res);
})();