js learn

concurRequest.ts

export async function concurRequest(urls: string[], maxNum: number = 0) {
    return new Promise((resolve, reject) => {
        const results: any[] = urls;
        if(urls.length === 0) {
            resolve(results);
            return;
        }
        let index = 0;
        let runing_count = 0;
        async function emit() {
            let item_id = index;
            console.log(item_id)
            index++;
            runing_count++;
            if(item_id < urls.length) {
                let res = await fetch(urls[item_id]);
                results[item_id] = res;
                runing_count--;
                emit();
            } else {
                runing_count--;
                if(runing_count == 1) {
                    resolve(results)
                }
            }
        }
        while(maxNum != 0 && runing_count < maxNum) //开始并发`
            emit();
    })
}