关于获取随机数字的练习

所选取数字的最大数字:<input type="number" id="max_num"><br>
    所选取数字的最小数字：<input type="number" id="min_num"><br>
    需要选取的个数：<input type="number" id="howMany"><br>
    获得的随机数字：<p id="getRandomNumber"></p><br>
    <input type="button" value="点击获取随机数" id="btn"><br>
    <script>
        var randomNumberArray = function () {
            var n = parseInt(document.getElementById("howMany").value);
            var minNum = parseInt(document.getElementById("min_num").value);
            var maxNum = parseInt(document.getElementById("max_num").value);
            var randomNumArr = [];
            for (var i = 0; i < n; i++) {
                var randomNum = (Math.floor(Math.random() * (maxNum - minNum + 1))) + minNum;
                while (randomNumArr.indexOf(randomNum) != -1) {
                    randomNum = (Math.floor(Math.random() * (maxNum - minNum + 1))) + minNum;
                }
                randomNumArr.push(randomNum);
            }
            return randomNumArr.sort(function (value1, value2) {
                return value1 - value2;
            })
        }

        var getNumAndShowThem = function () {
            document.getElementById("getRandomNumber").innerHTML = randomNumberArray();
        }
        document.getElementById("btn").addEventListener("click", getNumAndShowThem);

实现功能：

1.根据指定的区间以及指定的获取数字个数来获得随机数字。

2.所有随机数字不相同且按从小到大顺序排列。