Linked List in JavaScript

linked-list.js

// You can run this code by downloading it and typing in your console: node linked-list.js

// See the accompanying blog post here:
// And all of this is an ES6 adaptation of this excellent tutorial bu Cho S. Kim on CodeTuts: https://code.tutsplus.com/articles/data-structures-with-javascript-singly-linked-list-and-doubly-linked-list--cms-23392


// Create the object prototype for a "Node", that is, a list item (note that there is no technical relation to node.js or a "Node" in terms of the DOM)
class Node {
	constructor(data) {
		this.data = data;
		this.next = null;
	}
}

// Now create the prototype for the list that will hold references to the nodes
class SinglyList {
	constructor(length = 0, head = null) {
		// Underscores denote private variables and I don't entirely know how that's relevant here, but it was like that in the tutorial so whatever.
		this._length = length;
		this.head = head;
	}

	add(value) {
		// Get initial list values
		let length = this._length;
		let currentNode = this.head;

		// Create a new node
		let newNode = new Node(value);

		// Case 1: if nothing in list, create a node and set head to it
		if( !currentNode ) {
			this.head = newNode;
			this._length++;
			return newNode;
		}

		// Case 2: If the list is not empty (and implicitly has more than 1 item because only 2 or more items would have a currentNode.next)
		while( currentNode.next ) {
			currentNode = currentNode.next;
		}

		currentNode.next = newNode;
		this._length++;

		return newNode;
	}

	selectNodeAt(position) {
		let currentNode = this.head,
				length = this._length,
				count = 0,
				message = {failure: "Non existent node in this list!"};

		if(length === 0 || position < 0 || position > length)  {
			throw new Error(message.failure);
		}

		while (count < position) {
			currentNode = currentNode.next;
			count++;
		}

		return currentNode;
	}

	// Since we always operate on the head, this would remove the head
	remove(position) {
		let currentNode = this.head,
				length = this._length,
				count = 0,
				message = {failure: "Failure, no node to delete"},
				beforeToDelete = null,
				nodeToDelete = null,
				deletedNode = null;

		// Case 1: Throw and error if there is no node
		if(position < 0 || position > length) {
			throw new Error(message.failure);
		}

		// Case 2: If it's the first node
		if(position === 1) {
			this.head = currentNode.next; // Head is now at node after the one to be deleted
			deletedNode = currentNode;
			currentNode = null;
			this._length--;

			return deletedNode;
		}

		// Case 3: Any other node is selected to removed
		while(count < position) {
			beforeToDelete = currentNode;
			nodeToDelete = currentNode.next;
			count++;
		}

		beforeToDelete.next = nodeToDelete.next;
		deletedNode = nodeToDelete;
		nodeToDelete = null;
		this._length--;

		return deletedNode;

	}
}

// Test the list by creating one!
const list = new SinglyList();

list.add("hey");
list.add("ho");
list.add("hum");
list.add("bum");
list.remove(1); // Remove "hey"

// Note: We are printing the data of each node for readability's sake
console.log(list.head.data); // This should be "ho" since we have removed "hey"
console.log(list.selectNodeAt(1).data); // This will be "hum" since it is the first index after the head