add insertion sort

Author: polun

code/bubbleSort.js renamed to code/01.bubbleSort.js

@@ -12,6 +12,8 @@ function bubbleSort(arr) {
             }
         }
     }
+    
+    return arr;
 }
 
 util(bubbleSort);

code/selectionSort.js renamed to code/02.selectionSort.js

@@ -16,6 +16,8 @@ function selectionSort(arr) {
         arr[length - i - 1] = arr[flag];
         arr[flag] = temp;
     }
+
+    return arr;
 }
 
 util(selectionSort);

code/03.insertionSort.js

@@ -0,0 +1,24 @@
+const util = require('./util.js');
+
+function insertionSort(arr) {
+    const length = arr.length;
+
+    let prefixIndex,
+        current;
+
+    for (let i = 1; i < length; i++) {
+        prefixIndex = i - 1;
+        current = arr[i];
+        while (prefixIndex >= 0 && arr[prefixIndex] > current) {
+            arr[prefixIndex + 1] = arr[prefixIndex];
+
+            prefixIndex--;
+        }
+
+        arr[prefixIndex + 1] = current;
+    }
+
+    return arr;
+}
+
+util(insertionSort);

code/util.js

@@ -7,6 +7,5 @@ module.exports = function (sort) {
     console.log(arr);
     console.log('*'.repeat(20) + os.EOL);
 
-    sort(arr);
-    console.log(arr);
+    console.log(sort(arr));
 };