fix: merge sort in javascript (doocs#399)

* fix doocs#399
* thanks @Colin3191

Author: yanglbme

basic/sorting/MergeSort/MergeSort.js

@@ -9,11 +9,7 @@ function mergeSort(arr) {
 function merge(arr1, arr2) {
     let arr = [];
     while (arr1.length && arr2.length) {
-        if (arr1[0] < arr2[0]) {
-            arr.push(arr1.shift());
-        } else {
-            arr.push(arr2.shift());
-        }
+        arr.push(arr1[0] <= arr2[0] ? arr1.shift() : arr2.shift());
     }
     return [...arr, ...arr1, ...arr2];
 

basic/sorting/MergeSort/README.md

@@ -70,11 +70,7 @@ function mergeSort(arr) {
 function merge(arr1, arr2) {
     let arr = [];
     while (arr1.length && arr2.length) {
-        if (arr1[0] < arr2[0]) {
-            arr.push(arr1.shift());
-        } else {
-            arr.push(arr2.shift());
-        }
+        arr.push(arr1[0] <= arr2[0] ? arr1.shift() : arr2.shift());
     }
     return [...arr, ...arr1, ...arr2];