Answer 1

function multiRequest(urls = [], maxNum) {
    // 请求总数量
    const sum = urls.length;
    // 根据请求数量创建一个数组来保存请求的结果
    const result = new Array(sum).fill(false);
    // 当前完成的数量
    let count = 0;

    return new Promise((resolve, reject) => {
        // 请求maxNum个
        while (count < maxNum) {
            next();
        }
        function next() {
            let current = count++;
            // 处理边界条件
            if (current >= sum) {
                // 请求全部完成就将promise置为成功状态, 然后将result作为promise值返回
                !result.includes(false) && resolve(result);
                return;
            }
            const url = urls[current];
            console.log(`开始 ${current}`, new Date().toLocaleString());
            fetch(url).then(res => {
                // 保存请求结果
                result[current] = res;
                console.log(`完成 ${current}`, new Date().toLocaleString());
                // 请求没有全部完成, 就递归
                if (current < sum) {
                    next();
                }
            }).catch(err => {
                console.log(`结束 ${current}`, new Date().toLocaleString());
                result[current] = err;
                // 请求没有全部完成, 就递归
                if (current < sum) {
                    next();
                }
            });
        }
    });
}

const url = `https://www.baidu.com/s?wd=javascript`;
const urls = new Array(100).fill(url);

(async () => {
    const res = await multiRequest(urls, 10);
    console.log(res);
})();

Answer 2