Tree.js

function Node(data) {
    this.data = data;
    this.parent = null;
    this.children = [];
}

function Tree(data) {
    var node = new Node(data);
    this._root = node;
}

function Queue() {
    this.dataStore = []
    this.enqueue = function enqueue(element) {
        this.dataStore.push(element)
    }
    this.dequeue = function dequeue() {
        return this.dataStore.shift()
    }
    this.front = function front() {
        return this.dataStore[0]
    }
    this.back = function back() {
        return this.dataStore[this.dataStore.length - 1]
    }
}

Tree.prototype.add = function(data, toData, traversal) {
    var child = new Node(data)
      , parent = null
      , callback = function(node) {
        if (node.data === toData) {
            parent = node;
        }
    };

    this.contains(callback, traversal);

    if (parent) {
        parent.children.push(child);
        child.parent = parent;
    } else {
        throw new Error('Cannot add node to a non-existent parent.');
    }
};

Tree.prototype.traverseBF = function(callback) {
    var queue = new Queue();
 
    queue.enqueue(this._root);
 
    currentTree = queue.dequeue();
 
    while(currentTree){
        for (var i = 0, length = currentTree.children.length; i < length; i++) {
            queue.enqueue(currentTree.children[i]);
        }
 
        callback(currentTree);
        currentTree = queue.dequeue();
    }
};

Tree.prototype.contains = function(callback, traversal) {
    traversal.call(this, callback);
};

var tree = new Tree('CEO');
tree.add('Bill Gates', 'CEO', tree.traverseBF);
console.log(tree);