singlyLinkedList.js

class Node {
  constructor(value) {
    this.value = value;
    this.next = null;
  }
}

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

  push(value) {
    const newNode = new Node(value);
    if (!this.head) {
      this.head = newNode;
      this.tail = newNode;
    } else {
      this.tail.next = newNode;
      this.tail = newNode;
    }
    this.length++;
    return this;
  }

  pop() {
    if (this.length === 0) return undefined;
    let current = this.head;
    let newTail = this.head;
    while (current.next) {
      newTail = current;
      current = current.next;
    }
    this.tail = newTail;
    this.tail.next = null;
    this.length--;
    if (this.length === 0) {
      this.head = null;
      this.tail = null;
    }
    return current;
  }

  unshift(value) {
    const newNode = new Node(value);
    if (!this.head) {
      this.head = newNode;
      this.tail = newNode;
    } else {
      newNode.next = this.head;
      this.head = newNode;
    }
    this.length++;
    return this;
  }

  shift() {
    if (!this.head) return undefined;
    let currentHead = this.head;
    this.head = this.head.next;
    currentHead.next = null;
    this.length--;
    if (this.length === 0) {
      this.tail = null;
    }
    return currentHead;
  }

  get(index) {
    if (index < 0 || index >= this.length) return undefined;
    let current = this.head;
    for (let i = 0; i < index; i++) {
      current = current.next;
    }
    return current;
  }

  set(index, value) {
    let foundNode = this.get(index);
    if (foundNode) {
      foundNode.value = value;
      return true;
    }
    return false;
  }

  insert(index, value) {
    if (index < 0 || index > this.length) return false;
    if (index === 0) return !!this.unshift(value);
    if (index === this.length) return !!this.push(value);

    const newNode = new Node(value);
    const prevNode = this.get(index - 1);
    newNode.next = prevNode.next;
    prevNode.next = newNode;
    this.length++;
    return true;
  }

  remove(index) {
    if (index < 0 || index >= this.length) return undefined;
    if (index === 0) return this.shift();
    if (index === this.length - 1) return this.pop();

    const prevNode = this.get(index - 1);
    const removedNode = prevNode.next;
    prevNode.next = removedNode.next;
    removedNode.next = null;
    this.length--;
    return removedNode;
  }

  reverse() {
    if(this.length === 0) return undefined;
    
    let temp = this.head;
    this.head = this.tail;
    this.tail = temp;
    let next = temp.next;
    let prev = null;
    for (let i = 0; i < this.length; i++) {
      next = temp.next;
      temp.next = prev;
      prev = temp;
      temp = next;
    }
    return this;
  }
}

const myLinkedList = new LinkedList();
console.log(myLinkedList.push(1));
console.log(myLinkedList.push(2));
console.log(myLinkedList.push(3));

console.log(myLinkedList.pop());
console.log(myLinkedList.pop());

console.log(myLinkedList.unshift(2));
console.log(myLinkedList.unshift(3));

console.log(myLinkedList.shift());

console.log(myLinkedList.get(1));
console.log(myLinkedList.get(0));

console.log(myLinkedList.set(0, 1));
console.log(myLinkedList.set(1, 3));

console.log(myLinkedList.insert(1, 2));
console.log(myLinkedList.insert(3, 4));

console.log(myLinkedList.remove(3));
console.log(myLinkedList.remove(2));

console.log(myLinkedList.reverse());
console.log(myLinkedList.reverse());