added merge sort code in js

SortingAlgorithms/mergeSort.js

@@ -0,0 +1,35 @@
+function mergeSort(arr) {
+  if (arr.length <= 1) {
+    return arr;
+  }
+
+  const mid = Math.floor(arr.length / 2);
+  const left = mergeSort(arr.slice(0, mid));
+  const right = mergeSort(arr.slice(mid));
+
+  return merge(left, right);
+}
+
+function merge(left, right) {
+  let result = [];
+  let leftIndex = 0;
+  let rightIndex = 0;
+
+  while (leftIndex < left.length && rightIndex < right.length) {
+    if (left[leftIndex] < right[rightIndex]) {
+      result.push(left[leftIndex]);
+      leftIndex++;
+    } else {
+      result.push(right[rightIndex]);
+      rightIndex++;
+    }
+  }
+
+  // Concat remaining elements
+  return result.concat(left.slice(leftIndex)).concat(right.slice(rightIndex));
+}
+
+// Example usage
+const arr = [38, 27, 43, 3, 9, 82, 10];
+const sortedArray = mergeSort(arr);
+console.log(sortedArray);