LinkedList.js

class Node {
  constructor (data) {
    this.data = data
    this.nextNode = null
  }
}

class LinkedList {
  constructor(){
    this.head
  }

  isEmpty(){
    return !this.head ? true : false
  }

  insertAtHead(data){
    const node = new Node(data)
    node.nextNode = this.head

    this.head = node
  }

  insertAtTail(data) {
    if (this.isEmpty()){
      this.insertAtHead(data)
    }else {
      const node = new Node(data)
      let currentNode = this.head
    
      while(currentNode.nextNode){
        currentNode = currentNode.nextNode
      }

      currentNode.nextNode = node
    }
  }

  search(val){
    let currentNode = this.head
    while(currentNode){
      if(currentNode.data === val){
        console.log('Item found: ', currentNode);
        return true
      }
      currentNode = currentNode.nextNode
    }
    console.log('Item not found');
    return false
  }

  delete(val){
    if (this.isEmpty()){
      return
    }
    if (this.head.data === val){
      this.head = this.head.nextNode
    }else {
      let currentNode = this.head.nextNode
      let previousNode = this.head

      while(currentNode){
        if (currentNode.data === val) {
          previousNode.nextNode = currentNode.nextNode
        }
        previousNode = currentNode
        currentNode = currentNode.nextNode
      }
      return 
    }
    console.log('key not found');
  }

  findMidNode(){
    if (this.isEmpty()){
      console.log('List is empty')
    }

    let slowPointer = this.head
    let fastPointer = this.head.nextNode

    while(fastPointer && fastPointer.nextNode){
      fastPointer = fastPointer.nextNode.nextNode
      slowPointer = slowPointer.nextNode
    }
    
    console.log('Middle of list is: ', slowPointer.data);
    return slowPointer
  }

  print(){
    if (this.isEmpty()){
      console.log('List is empty')
      
    } else {
      let currentNode = this.head
      const items = []
      while(currentNode){
        items.push(currentNode.data)
        currentNode = currentNode.nextNode
      }
      console.log(items.join('->'))
    }

  }
}



const list = new LinkedList()
list.insertAtHead(50)
list.insertAtHead(15)
list.insertAtHead(35)
list.insertAtTail(5)
list.insertAtTail(15)

list.insertAtTail(25)

list.print()
list.findMidNode()