singly-linked-list.js

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

class linkedList {
  #size = 0;
  #head = null;
  constructor() {
    this.#size = 0;
    this.#head = null;
  }

  length() {
    return this.#size;
  }

  get(index) {
    let curr = this.#head
    let count = 0
    while(count < index) {
      curr = curr.next
      count++
    }
    return curr.val
  }

  append(val) {
    this.#size += 1;
    let node = new Node(val);

    if (this.#head == null) {
      this.#head = node;
    } else {
      let curr = this.#head;

      while (curr.next !== null) {
        curr = curr.next;
      }
      curr.next = node;
    }
  }

  prepend(val) {
    this.#size += 1;
    let node = new Node(val);

    let curr = this.#head;
    node.next = curr;
    this.#head = node;
  }

  insertAt(val, index) {
    if (index > this.#size) throw new Error('Index is out of bound');

    let count = 1;
    let curr = this.#head;
    let node = new Node(val);

    if (index == 0) {
      this.prepend(val);
      return;
    }

    while (curr.next) {
      if (count == index) break;
      curr = curr.next;
      count++;
    }

    node.next = curr.next;
    curr.next = node;
    this.#size += 1;
  }

  removeAt(index) {
    let count = 1;
    let curr = this.#head;
    
    if(index >= this.#size) throw new Error('Index is out of bound')
    if(index == 0) {
      this.#head = this.#head.next
      this.#size-=1
      return
    }

    while (curr.next && count < index) {
      curr = curr.next;
      count++
    }
    curr.next = curr.next.next;
    this.#size-=1
  }

  entries() {
    let temp = [];
    let curr = this.#head;
    while (curr.next) {
      temp.push(curr.val);
      curr = curr.next;
    }
    temp.push(curr.val);
    return temp;
  }
}

const ll = new linkedList();
ll.append(1);
ll.append(2);
ll.append(3);
ll.prepend(5);
ll.prepend(50);
ll.insertAt(25, 5);
ll.insertAt(20, 0);
ll.insertAt(30, 6);
console.log(ll.entries());
console.log('val at idx 6: ',ll.get(6))
ll.removeAt(0);
console.log(ll.entries());
console.log('len: ',ll.length());