Round 1 interview question, potential answer

Taxonomy tree 1 parent node

/*
    value String
    children []Node
*/
function Node(value, children) {
    self.value = value;
    self.children = children;
}
/*
    root Node
*/
function Tree(root) {
    self.root = root;
    
    /*
        value String
        depth Integer
        node Node
    */
    var insertAt = function(value, depth, node) {
        if (depth < 0) {
            throw new Error();
        } else if (depth === 0) {
            return new Node(value, [node]);
        } else if (depth === 1) {
            return new Node(node.value, [new Node(value, node.children)]);
        } else {
            var children = [];
            for (var i = 0; i < node.children.length; i++) {
                children += insertAt(value, depth - 1, node.children[i]);  
            }
            return new Node(node.value, children);
        }
    }
}

/*
    value String
    depth Integer
*/
Tree.prototype.insert = function(value, depth) {
    self.root = insertAt(value, depth, self.root);
    return self.root;
}