Initial Doubly Linked List

src/doubly_linked_list.js

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+import { default as createDoublyLinkedNode } from './add_doubly_linked_node';
+
+// Doubly Linked List
+
+export default function DoublyLinkedList() {
+    return {
+        head: null,
+        tail: null,
+        length: 0,
+        isEmpty() {
+            return this.length == 0;
+        },
+        insertHead(value) {
+            let node = createDoublyLinkedNode(value);
+            if (this.head == null) {
+                this.head = node;
+                this.tail = node;
+                this.length++;
+                return node;
+            } else {
+                this.head.previous = node;
+                node.next = this.head;
+                this.head = node;
+                this.length++;
+                return node;
+            }
+        },
+        insertTail() {},
+        insertAt() {},
+        getItemAt() {},
+        removeHead() {},
+        removeTail() {},
+        removeFrom() {},
+        print() {
+            let current = this.head;
+            let listStr = '';
+
+            while (current) {
+                listStr += current.value + (current.next ? ', ' : '');
+                current = current.next;
+            }
+
+            return listStr;
+        }
+    };
+}