Javascriptの二重リンクリストクラス

例

class DoublyLinkedList {
   constructor() {
      this.head = null;
      this.tail = null;
      this.length = 0;
   }
   insert(data, position = this.length) {
      let node = new this.Node(data);
      // List is currently empty
      if (this.head === null) {
         this.head = node;
         this.tail = node;
         this.length++;
         return this.head;
      }
      // Insertion at head
      if (position == 0) {
         node.prev = null;
         node.next = this.head;
         this.head.prev = node;
         this.head = node;
         return this.head;
      }
      let iter = 1;
      let currNode = this.head;
      while (currNode.next != null && iter < position) {
         currNode = currNode.next; iter++;
      }
      // Make new node point to next node in list
      node.next = currNode.next;
      // Make next node's previous point to new
      node if (currNode.next != null) {
         currNode.next.prev = node;
      }
      // Make our node point to previous node
      node.prev = currNode;

      // Make previous node's next point to new node
      currNode.next = node;

      // check if inserted element was at the tail, if yes then make tail point to it
      if (this.tail.next != null) {
         this.tail = this.tail.next;
      }
      this.length++;
      return node;
   }
   remove(data, position = 0) {
      if (this.length === 0) {
         console.log("List is already empty");
         return;
      }
      this.length--;
      let currNode = this.head;
      if (position <= 0) {
         this.head = this.head.next;
         this.head.prev = null;
      } else if (position >= this.length - 1) {
         this.tail = this.tail.prev;
         this.tail.next = null;
      } else {
         let iter = 0;
         while (iter < position) {
            currNode = currNode.next;
            iter++;
         }
         currNode.next = currNode.next.next;
         currNode.next.prev = currNode;
      }
      return currNode;
   }
   display() {
      let currNode = this.head;
      while (currNode != null) {
         console.log(currNode.data + " <-> ");
         currNode = currNode.next;
      }
   }
}

DoublyLinkedList.prototype.Node = class {
   constructor(data) {
      this.data = data;
      this.next = null;
      this.prev = null;
   }
};