Update 3.insertionSort.md

fixed: js bug

Author: Rain120

3.insertionSort.md

@@ -23,12 +23,13 @@
 function insertionSort(arr) {
     var preIndex;
     for (var i = 1; i < arr.length; i++) {
+    	var current = arr[i];
         preIndex = i - 1;
         while(preIndex >= 0 && arr[preIndex] > arr[i]) {
             arr[preIndex + 1] = arr[preIndex];
             preIndex--;
         }
-        arr[preIndex + 1] = arr[i];
+        arr[preIndex + 1] = current;
     }
     return arr;
 }