linked_list.js

/*
const x = new LinkedList();

x.add('meme');
x.add('dream');
x.lastValue; // 'dream'
*/

class LinkedItem {
  constructor(value, next) {
    if (typeof value !== 'undefined') this.value = value;
    if (typeof next !== 'undefined') this.next = next;
  }
  
  get hasNext() {
    return typeof this.next !== 'undefined';
  }
}

class LinkedList {
  constructor() {
    this.first = null;
  }
  
  add(value) {
    if (this.first) {
      this.lastItem.next = new LinkedItem(value);
    } else {
      this.first = new LinkedItem(value);
    }
    return true;
  }
  
  remove(index) {
    if (!this.first) return false;
    let current = this.first;
    let deleted = null;
    if (index === 1) {
      this.first = current.next;
      deleted = current;
      current = null;
    } else {
      let beforeDelete = getItem(index - 1);
      let deleted = beforeDelete.next;
      beforeDelete.next = deleted.next;
    }
    
    return deleted;
  }
  
  get lastItem() {
    if (!this.first) return null;
    let current = this.first;
    while (current.hasNext) current = current.next;
    return current;
  }
  
  get lastValue() {
    if (!this.first) return null;
    return this.lastItem.value;
  }
  
  get firstItem() {
    return this.first;
  }
  
  get firstValue() {
    if (!this.first) return null;
    return this.first.value;
  }
  
  getItem(index) {
    if (!this.first) return null;
    let count = 0;
    let current = this.first;
    while (index < count) {
      current = current.next;
      count++;
    }
    return current;
  }
  
  getValue(index) {
    if (!this.first) return null;
    return this.getItem(index).value;
  }
}