@vanillaes/computer-science/src/LinkedList/LinkedList.js

Algorithms and Data Structures implemented in modern JS

/** A LinkedList implementation using nodes liked by reference */
export class LinkedList {
  /**
   * The head node in the list
   * @private
   * @type {Object}
   */
  #head = null

  /**
   * The tail node in the list
   * @private
   * @type {Object}
   */
  #tail = null

  /**
   * The number of items in the list
   * @type {number}
   */
  size = 0

  /**
   * @param {array} [items] an array of items to add to the list
   */
  constructor (items) {
    if (items) {
      this.addAll(items)
    }
  }

  /**
   * Add an item to the list
   *
   * @param {*} item an item to add to the list
   */
  add (item = null) {
    if (item === null) { throw Error('\'item\' parameter not defined') }
    if (this.size === 0) {
      this.#tail = new ListNode(item, null)
      this.#head = this.#tail
    } else {
      const prev = this.#tail
      this.#tail = new ListNode(item, null)
      prev.next = this.#tail
    }
    this.size++
  }

  /**
   * Add multiple items to the list
   *
   * @param {*[]} items an array of items to be added to the list
   */
  addAll (items = null) {
    if (items === null) { throw Error('\'items\' parameter not defined') }

    items.forEach(item => this.add(item))
  }

  /**
   * Remove an item from the list
   *
   * @param {*} item the item to remove from the list
   * @returns {boolean} true if the item was successfully removed, false if not
   */
  remove (item = null) {
    if (item === null) { throw Error('\'item\' parameter not defined') }
    if (this.size === 0) { throw Error('can\'t remove an item from an empty list') }

    let prev = this.#head
    let curr = this.#head
    while (curr != null) {
      if (curr.data === item) {
        if (this.size === 1) { // remove the last remaining element
          this.#head = null
          this.tail = null
        } else if (curr === this.#head) { // remove first element
          this.#head = this.#head.next
        } else if (curr === this.#tail) { // remove last element
          this.#tail = prev
          this.#tail.next = null
        } else { // remove element
          prev.next = curr.next
        }
        this.size--

        return true
      }
      prev = curr
      curr = prev.next
    }

    return false
  }

  /**
   * Remove all items from the list
   * @method
   */
  clear () {
    this.#head = null
    this.#tail = null
    this.size = 0
  }

  /**
   * Iterate all items (in-order) in the list
   *
   * @private
   * @returns {Iterator<*>} an iterator for the data
   */
  [Symbol.iterator] () {
    let item = this.#head
    return {
      next: () => {
        if (item) {
          const value = item.data
          item = item.next
          return { value, done: false }
        }

        return { value: null, done: true }
      }
    }
  }
}

/**
 * @private
 */
class ListNode {
  data
  next

  constructor (data, next = null) {
    this.data = data
    this.next = next
  }
}