Patch 5 (trekhleb#127)

* New function 'fromArray'

Function get array of Doubly Linked List Nodes, go through and append to currently list.

* New Test for new function 'fromArray'

* Minor changes

Minor changes about coding style.

Author: seIncorp

src/data-structures/doubly-linked-list/DoublyLinkedList.js

@@ -213,6 +213,15 @@ export default class DoublyLinkedList {
     return nodes;
   }
 
+  /**
+   * @param {DoublyLinkedListNode[]} array - Array of nodes
+   * @return {DoublyLinkedListNode[]}
+   */
+  fromArray(arr = []) {
+    arr.forEach(node => this.append(node.value));
+    return this;
+  }
+
   /**
    * @param {function} [callback]
    * @return {string}

src/data-structures/doubly-linked-list/__test__/DoublyLinkedList.test.js

@@ -36,6 +36,23 @@ describe('DoublyLinkedList', () => {
     expect(linkedList.toString()).toBe('3,2,1');
   });
 
+  it('should append new nodes from array', () => {
+    const linkedList1 = new DoublyLinkedList();
+    linkedList1.append(1);
+    linkedList1.append(1);
+    linkedList1.append(2);
+    linkedList1.append(3);
+    linkedList1.append(3);
+    linkedList1.append(3);
+    linkedList1.append(4);
+    linkedList1.append(5);
+    const array = linkedList1.toArray();
+
+    const linkedList2 = new DoublyLinkedList();
+    linkedList2.fromArray(array);
+    expect(linkedList2.toString()).toBe('1,1,2,3,3,3,4,5');
+  });
+
   it('should delete node by value from linked list', () => {
     const linkedList = new DoublyLinkedList();