4. Median of Two Sorted Arrays

There are two sorted arrays nums1 and nums2 of size m and n respectively.
You may assume nums1 and nums2 cannot be both empty.
Example 1:
nums1 = [1, 3]
nums2 = [2]
The median is 2.0

Example 2:
nums1 = [1, 2]
nums2 = [3, 4]
The median is (2 + 3)/2 = 2.5
思路：把两个数组连接起来，按从小到大的顺序形成新的数组，然后根据数组的长度找中间值。如果长度是偶数，中间值为中间两个数的平均值，如果是奇数，则是中间那个数。

  /**
   * @param {number[]} nums1
   * @param {number[]} nums2
   * @return {number}
   */
  var findMedianSortedArrays = function(nums1, nums2) {
      var arr = nums1.concat(nums2);
      var numsArr = arr.sort(function sequence(a,b){
           return a - b;
      });
      var len = numsArr.length;
      var middle = 0;
      if(len%2 == 0) {
          middle = (numsArr[parseInt(len/2)]+numsArr[parseInt(len/2)-1])/2;
      } else {
          middle = numsArr[parseInt(len/2)]
      }
      return middle;
  };