LinkedList ES6 Implementation

LinkedList.js

class LinkedList {
  constructor() {
    this.head = null;
    this.tail = null;
    this.count = 0;
  }

  get length() {
    return this.count;
  }

  addLast(data) {
    // Create a new Node
    const node = {
      data: data,
      next: null
    };

    if (this.count === 0) {
      // If this is the first Node, assign it to head
      this.head = node;
    } else {
      // If not the first node, link it to the last node
      this.tail.next = node;
    }

    this.tail = node;

    this.count++;
  }

  addFirst(data) {
    // Create a new Node
    const node = {
      data: data,
      next: null
    };

    // Save the first Node
    const temp = this.head;

    // Point head to the new Node
    this.head = node;

    // Add the rest of node behind the new first Node
    this.head.next = temp;

    this.count++;

    if (this.count === 1) {
      // If first node,
      // point tail to it as well
      this.tail = this.head;
    }
  }

  removeFirst() {
    if (this.count > 0) {
      // The head should point to the second element
      this.head = this.head.next;

      this.count--;

      if (this.count === 0) {
        // If list empty, set tail to null
        this.tail = null;
      }
    }
  }

  removeLast() {
    if (this.count > 0) {
      if (this.count === 1) {
        this.head = null;
        this.tail = null;
      } else {
        // Find the Node right before the last Node
        let current = this.head;
        while (current.next !== this.tail) {
          current = current.next;
        }

        current.next = null;
        this.tail = current;
      }
      this.count--;
    }
  }

  indexOf(value) {
    let index = 0;
    let current = this.head;

    while (current !== null) {
      if (current.data === value) return index;
      current = current.next;
      index++;
    }
    return -1;
  }

  contains(value) {
    return this.indexOf(value) !== -1;
  }

  // OR:
  //   contains(value) {
  //     let current = this.head;
  //     while (current !== null) {
  //       if (current.data === value) return true;
  //       current = current.next;
  //     }
  //     return false;
  //   }
  // }

  //This method converts the linked list to an array
  toArray() {
    let current = this.head;
    let array = [];
    let index = 0;
    while (current !== null) {
      array[index++] = current.data;
      current = current.next;
    }
    return array;
  }
}