A Javascript implementation of a Singly-Linked List

SinglyLinkedList.js

function Node(data) {
  this.data = data;
  this.next = null;
}

function SinglyList() {
  this._length = 0;
  this.head = null;
}

SinglyList.prototype.add = function(value) {
  let node = new Node(value),
      currentNode = this.head;
  if (!currentNode) {
    this.head = node;
    this._length += 1;
    return node;
  }
  
  while (currentNode.next) {
    currentNode = currentNode.next; 
  }
  
  currentNode.next = node;
  this._length += 1;
  return node;
};

SinglyList.prototype.searchNodeAt = function(position) {
    let currentNode = this.head,
        length = this._length,
        count = 1;
  if (length === 0 || position < 1 || position > length) {
    throw new Error("Non-existent node in this list");
  }
  
  while (count < position) {
    currentNode = currentNode.next;
    count++;
  }
  
  return currentNode;
};

SinglyList.prototype.remove = function(position) {
  let currentNode = this.head,
      length = this._length,
      count = 1,
      beforeNodeToDelete = null,
      deletedNode = null;
  
  if (position < 0 || position > length || length === 0) {
    throw new Error("Non-existent node in list");
  }
  
  if (position === 1) {
    this.head = currentNode.next;
    deletedNode = currentNode;
    currentNode = null;
    this._length -= 1;
    return deletedNode;
  }
  
  while (count < position) {
    beforeNodeToDelete = currentNode;
    currentNode = currentNode.next;
    count++;
  }
  
  beforeNodeToDelete.next = currentNode.next;
  deletedNode = currentNode;
  currentNode = null;
  this._length -= 1;
  return deletedNode;
};