Answer 1

所以到底处于什么状态？

Answer 2

function multiRequest(urls, maxNum) {
    return new Promise((resolve, reject) => {
        const result = Array(urls.length);
        let resNum = 0;
        let promiseIndex = 0;

        while (promiseIndex < maxNum) {
            genNextFetch();
        }

        function genNextFetch() {
            if (promiseIndex >= urls.length) return;
            const curIndex = promiseIndex++;
            fetch(urls[curIndex])
                .then((res) => {
                    result[curIndex] = res;
                    resNum += 1;
                    if (resNum === urls.length) {
                        resolve(result);
                    } else {
                        genNextFetch();
                    }
                })
                .catch((err) => {
                    reject(err);
                });
        }
    });
}

Answer 3

哈哈哈懂了，谢谢两位的回答~