JS案例：数组相关

1、数组倒置

<script>
        var arr = [1, 2, 3, 4, 5, 6, 7, 8, 9]
        var newArr = []
        for (i = arr.length - 1; i >= 0; i--) {
            newArr[newArr.length] = arr[i]
        }
        console.log(newArr)
</script>

2、数组去重

  <script>
        function unique(arr) {
            var newArr = []
            for (var i = 0; i < arr.length; i++) {
                if (newArr.indexOf(arr[i]) === -1) {
                    newArr.push(arr[i])
                }
            }
            return newArr
        }
        var demo = unique(['a', 'b', 'b', 'c', 'd'])
        console.log(demo)
    </script>

3、随机点名

<script>
        function getRandom(x, y) {
            var sub = Math.abs(y - x)
            return Math.floor(Math.random() * (sub + 1)) + Math.min(x, y)
        }
        // console.log(getRandom(0, 10))


        /*         var arr = ["小赵", "小钱", "小孙", "小李", "小周", "小吴", "小郑", "小王", "小冯", "小陈", "小朱", "小魏"]
                var ran = arr[Math.floor(Math.random() * ((arr.length - 1) + 1))]
                console.log(ran);
                document.write(ran) */
        var arr = ["小赵", "小钱", "小孙", "小李", "小周", "小吴", "小郑", "小王", "小冯", "小陈", "小朱", "小魏"]
        var y = arr.length - 1
        var x = 0
        console.log(arr[getRandom(0, y)])
    </script>