17 第三大的数

<script>
        function thirdnum(nums) {
            // console.log(nums)
            nums = [...new Set([...nums])]
            nums = nums.sort((a,b)=>b-a)
            // console.log(nums)
            if (nums.length >= 3) {
                console.log(nums[2])
                return nums[2]
            } else {
                return Math.max(...nums)
            }
        }
        var arr = [1,5,9,5]
        thirdnum(arr)
    </script>