Answer 1

    function multiRequest(urls, maxNum, callback) {
		var arr = [];
		var count = 0;
		for (let i = 0; i < maxNum; i++) {
			ajax(i)
		}
		function ajax(i) {
			if (urls[i] !== undefined && urls[i] !== null) {
				setTimeout(function () {
					count++;
					success(urls[i], i)
				}, Math.random() * 10000)
			}
		}
		function success(res, i) {
			arr[i] = res;
			if (count === urls.length) {
				callback(arr);
			} else {
				let index = maxNum + count - 1
				ajax(index)
			}
		}
	}

Answer 2

厉害

Answer 3

_围观男神装逼！！！！_吓得我打字都歪了