Tree data structure implementation

tree.js

/***
 * Tree Data Structure Implementation
 */

/**
 * Generates a tree
 * @param {String} data
 * @return {Object} Tree
 */
function Tree(data) {
	this._root = new Node(data);
}

/**
 * Generates a node
 * @param {String} data
 * @return {Object} Node
 */
function Node(data) {
	this.data = data;
	this.parent = null;
	this.children = [];
}

/**
 * Traverses the tree depth-first
 * @param {Function} callback
 */
Tree.prototype.traverseDF = function(callback){
	function traverse(currentNode){
		for(let i = 0; i < currentNode.children.length; i++){
			traverse(currentNode.children[i]);
		}
		callback(currentNode);
	}
	traverse(this._root);
}

/**
 * Adds a new node to the tree
 * @param {String} newData
 * @param {String} parentData
 */
Tree.prototype.add = function(newData, parentData){
	let nodeParent = null;
	this.traverseDF(node=>{
		if(node.data === parentData){
			nodeParent = node;
		}
	});
	let newNode = new Node(newData);
	nodeParent.children[nodeParent.children.length] = newNode;
	newNode.parent = nodeParent;
}

/**
 * Removes a node from the tree
 * @param {String} data
 * @param {String} parentData
 */
Tree.prototype.remove = function(data, parentData){
	let nodeParent = null;
	this.traverseDF(node=>{
		if(node.data === parentData){
			nodeParent = node;
		}
	});
	let removeNode = nodeParent.children.filter(node=>node.data === data)[0];
	nodeParent.children.splice(nodeParent.children.indexOf(removeNode),1);
}

/**
 * Runs all tests
 */
function tests(){
	var tree = new Tree("one");
	if(!tree._root){
		console.warn("Test failed: _root does not exist");
	}

	tree.add("two","one");
	tree.add("three","one");
	if(tree._root.children.length !== 2){
		console.warn("Test failed: children were not added to root")
	}

	tree.add("four","two");
	tree.add("five","two");
	tree.add("six","four");
	let allNodes = [];
	tree.traverseDF(node=>{
		allNodes.push(node);
	});
	if(allNodes.length !== 6){
		console.warn("Test failed: all nodes not counted");
	}

	tree.remove("two","one");
	if(tree._root.children.length !== 1){
		console.warn("Test failed: child node was not removed from root");
	}
}

tests();