--update : add doubly link list

Author: TheSTL

src/_DataStructures_/DoublyLinkedList/index.js

@@ -0,0 +1,68 @@
+/* eslint-disable class-methods-use-this */
+class Node {
+  constructor(data, previous, next) {
+    this.data = data;
+    this.previous = previous;
+    this.next = next;
+  }
+}
+
+class DoublyLinkedList {
+  constructor() {
+    // head -> tail
+    // head <- tail
+    this.head = new Node(null, null, null);
+    this.tail = new Node(null, null, null);
+    this.head.next = this.tail; // head next point to tail
+    this.tail.previous = this.head; // tail previous point to head
+  }
+
+  addAtBeginning(value) {
+    const newNode = new Node(value, this.head, this.head.next);
+    this.head.next.previous = newNode;
+    this.head.next = newNode;
+  }
+
+  addAtEnd(value) {
+    const newNode = new Node(value, this.tail.previous, this.tail);
+    this.tail.previous.next = newNode;
+    this.tail.previous = newNode;
+  }
+
+  removeAtBeginning() {
+    this.remove(this.head.next);
+  }
+
+  removeAtEnd() {
+    this.remove(this.tail.previous);
+  }
+
+  remove(node) {
+    const previousNode = node.previous;
+    const nextNode = node.next;
+    previousNode.next = nextNode;
+    nextNode.previous = previousNode;
+  }
+
+  length() {
+    let address = this.head.next;
+    let count = 0;
+    while (address !== this.tail) {
+      count += 1;
+      address = address.next;
+    }
+    return count;
+  }
+
+  display() {
+    let address = this.head.next;
+    while (address !== this.tail) {
+      console.log(address.data);
+      address = address.next;
+    }
+  }
+}
+
+module.exports = {
+  DoublyLinkedList,
+};