Leetcode 3Sum Closest JS implementation

Given an array S of n integers, find three integers in s such so the sum is closest to a Given number, target. Return the sum of the three integers. You may assume this each input would have exactly one solution.

For example, given array S = {-1 2 1-4}, and target = 1.

The sum is closest to the target is 2. (-1 + 2 + 1 = 2).

 Comparison function functions Sortnum (a,b) {return a-b; var threesumclosest = function (Nums, target) {switch (nums.length) {case 0:re  
        Turn 0;  
        Case 1:return Nums[0];  
        Case 2:return Nums[0]+nums[1];  
        Default:break;
    } var k=nums.length-1;   var arrnum=nums.sort (Sortnum);   First the array of the order of Var currentsum=arrnum[0]+arrnum[1]+arrnum[2];
    Given the initial comparison value Var Closesum=currentsum;  

        var diff =math.abs (Currentsum-target);  
           for (var i = 0; i < k-1 i++)////Set first number first and the last number, if three number of and greater than the target value, then k minus 1; if less than the target value plus 1;j and K values are equal, then I plus 1, into the outer layer next cycle, K value must be reset;     K=nums.length-1;  
            K to reset for (var j = i+1 J < K;)  
                {currentsum = Arrnum[i] + arrnum[j] + arrnum[k];  
                if (currentsum = = target) {return currentsum; } if (Math.Abs (currentsum-target) < diff) {closesum = Currentsum;  
                diff = Math.Abs (currentsum-target);  
                } if (Currentsum < target) {j + +;  
                else {k--;
}} return closesum; };