JS: Tree Implementation

tree.js

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

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

Tree.prototype.traverseDF = function(cb) {
   (function recurse(current) {
       for(var i = 0; i < current.children.length; i++) {
           recurse(current.children[i]);
       }

       cb(current);
   })(this._root)
};

Tree.prototype.traverseBF = function(cb) {
    var queue = [];
    queue.push(this._root);
    current = queue.shift();

    while(current) {
        for(var i = 0; i < current.children.length; i++) {
            queue.push(current.children[i]);
        }
        cb(current);
        current = queue.shift();
    }
};

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

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.remove = function(data, fromData, traversal) {
    var tree = this,
        parent = null,
        childToRemove = null,
        index;
 
    var callback = function(node) {
        if (node.data === fromData) {
            parent = node;
        }
    };
 
    this.contains(callback, traversal);
 
    if (parent) {
        index = parent.children.indexOf(data);
 
        if (index === undefined) {
            throw new Error('Node to remove does not exist.');
        } else {
            childToRemove = parent.children.splice(index, 1);
        }
    } else {
        throw new Error('Parent does not exist.');
    }
 
    return childToRemove;
};

var tree = new Tree('one');
 
tree._root.children.push(new Node('two'));
tree._root.children[0].parent = tree;
 
tree._root.children.push(new Node('three'));
tree._root.children[1].parent = tree;
 
tree._root.children.push(new Node('four'));
tree._root.children[2].parent = tree;
 
tree._root.children[0].children.push(new Node('five'));
tree._root.children[0].children[0].parent = tree._root.children[0];
 
tree._root.children[0].children.push(new Node('six'));
tree._root.children[0].children[1].parent = tree._root.children[0];
 
tree._root.children[2].children.push(new Node('seven'));
tree._root.children[2].children[0].parent = tree._root.children[2];
 
/*
 
creates this tree
 
 one
 ├── two
 │   ├── five
 │   └── six
 ├── three
 └── four
     └── seven
 
*/
// tree.traverseDF(it => console.log(it.data));
// tree.traverseBF(it => console.log(it.data));
// console.dir(tree);