Create 0912-sort-an-array.js

Added solution for Sorting an array in JS.

javascript/0912-sort-an-array.js

@@ -0,0 +1,54 @@
+/**
+ * https://leetcode.com/problems/sort-an-array/
+ * Merge Sort
+ * Time O(n*log(n)) | Space O(n)
+ * @param {number[]} nums
+ * @return {number[]}
+ */
+var sortArray = function(nums) {
+
+ const merge = (left, mid, right) => {
+ const arr1 = nums.slice(left, mid+1);
+ const arr2 = nums.slice(mid+1, right + 1);
+
+ let p1 = 0; 
+ let p2 = 0;
+ let gp = left;
+
+ while(p1 < arr1.length && p2 < arr2.length) {
+ if(arr1[p1] < arr2[p2]) {
+ nums[gp] = arr1[p1];
+ p1++;
+ } else {
+ nums[gp] = arr2[p2];
+ p2++;
+ }
+ gp++;
+ }
+
+ while(p1 < arr1.length) {
+ nums[gp] = arr1[p1];
+ p1++;
+ gp++;
+ }
+
+ while(p2 < arr2.length) {
+ nums[gp] = arr2[p2];
+ p2++;
+ gp++;
+ }
+ return nums;
+ } 
+
+ const mergeSort = (left, right) => {
+
+ if(left === right) return nums;
+
+ const mid = Math.floor((left+right)/2);
+ mergeSort(left, mid);
+ mergeSort(mid+1, right);
+ return merge(left, mid, right);
+ }
+
+ return mergeSort(0, nums.length - 1);
+};