another-linked-list/src/linked-list.js

Linked list in JavaScript

/**
 * @description implementation of Linked List
 * @module LinkedList
 */

import LinkedListNode from './linked-list-node';

export default class LinkedList {
  /**
   * @description class constructor
   */
  constructor() {
    this.head = null;
    this.tail = null;
  }

  /**
   * @public method
   * @description prepend value to linked list
   * @param {*} value
   * @return {LinkedList}
   */
  prepend(value) {
    const newNode = new LinkedListNode(value, this.head);
    this.head = newNode;

    if (!this.tail) {
      this.tail = newNode;
    }

    return this;
  }

  /**
   * @public method
   * @description append value to linked list
   * @param {*} value
   * @return {LinkedList}
   */
  append(value) {
    const newNode = new LinkedListNode(value);

    if (!this.head) {
      this.head = newNode;
      this.tail = newNode;

      return this;
    }

    const currentTail = this.tail;
    currentTail.next = newNode;
    this.tail = newNode;

    return this;
  }

  /**
   * @public method
   * @description delete value from linked list node
   * @param {*} value
   * @return {LinkedListNode}
   */
  delete(value) {
    if (!this.head) {
      return null;
    }

    let deletedNode = null;

    while (this.head && this.head.value === value) {
      deletedNode = this.head;
      this.head = this.head.next;
    }

    let currentNode = this.head;

    if (currentNode !== null) {
      while (currentNode.next) {
        if (currentNode.next.value === value) {
          deletedNode = currentNode.next;
          currentNode.next = currentNode.next.next;
        } else {
          currentNode = currentNode.next;
        }
      }
    }

    if (this.tail.value === value) {
      this.tail = currentNode;
    }

    return deletedNode;
  }

  /**
   * @public method
   * @description delete tail value from linked list node
   * @return {LinkedListNode}
   */
  deleteTail() {
    const deletedTail = this.tail;

    if (this.head === this.tail) {
      this.head = null;
      this.tail = null;

      return deletedTail;
    }

    let currentNode = this.head;
    while (currentNode.next) {
      if (!currentNode.next.next) {
        currentNode.next = null;
      } else {
        currentNode = currentNode.next;
      }
    }

    this.tail = currentNode;

    return deletedTail;
  }

  /**
   * @public method
   * @description delete head value from linked list
   * @return {LinkedListNode}
   */
  deleteHead() {
    if (!this.head) {
      return null;
    }

    const deletedHead = this.head;

    if (this.head.next) {
      this.head = this.head.next;
    } else {
      this.head = null;
      this.tail = null;
    }

    return deletedHead;
  }

  /**
   * @public method
   * @description find value in linked list
   * @param {Object} findParams
   * @param {function} [findParams.callback]
   * @return {LinkedListNode}
   */
  find({ value = undefined, callback = undefined }) {
    if (!this.head) {
      return null;
    }

    let currentNode = this.head;

    while (currentNode) {
      if (callback && callback(currentNode.value)) {
        return currentNode;
      }

      if (value !== undefined && currentNode.value === value) {
        return currentNode;
      }

      currentNode = currentNode.next;
    }

    return null;
  }

  /**
   * @public method
   * @description convert linked list to array
   * @return {LinkedListNode[]}
   */
  toArray() {
    const nodes = [];

    let currentNode = this.head;
    while (currentNode) {
      nodes.push(currentNode);
      currentNode = currentNode.next;
    }

    return nodes;
  }

  /**
   * @public method
   * @description convert linked list to string
   * @param {function} [callback]
   * @return {string}
   */
  toString(callback) {
    return this.toArray().map(node => node.toString(callback)).toString();
  }
}