Singly linked list in JS

linkedList.js

const LinkedList = () => {
  let _list = {
    head: null,
    tail: null,
    length: 0
  }

  // Node creator
  let Node = (data) => { 
    let node = {
      data: data,
      next: null
    };
    return node
  }

  return {  // Public methods

    // Add node to tail (last element)
    push (data) {  
      let node = Node(data)
      if (!_list.head) {
        _list.head = node
        _list.tail = node

      } else {
        _list.tail.next = node
        _list.tail = node
      }
      
      _list.length++
    },

    // Remove last node (tail)
    pop () {  
      if (_list.length == 0) {
        throw new Error('List has no elements')
      } else {
        let tempNode = _list.head
        while(tempNode.next.next) { // Last node (tail) has next = null;
          tempNode = tempNode.next
        }
        tempNode.next = null;
        _list.length--
      }    
    },

    // Add node to head (first element)
    unshift (data) {  
      let node = Node(data)
      if (!_list.head) {
        _list.head = node
        _list.tail = node

      } else {
        let currentHead = _list.head
        _list.head = node
        _list.head.next = currentHead
      }
      
      _list.length++
    },

    // Remove first node (head)
    shift () {  
      if (_list.length == 0) {
        throw new Error('List has no elements')
      } else {
        let currentHead = _list.head
        _list.head = currentHead.next
        _list.length--
      }
    },

    size () {
      return _list.length
    },

    elements () {
      return _list.head
    }
  }
}