Find length of binary tree

Length of binary tree or height of binary tree is maximum no of nodes from root down to leaf nodes.

So if a length at left side or right side is greater with comparision to each other then greater value will be the length.

class Node {
    constructor(value) {
        this.data = value;
        this.left = null;
        this.right = null;
    }
}
class BinaryTree {
    add(value) {
        const node = new Node(value);
        let pointer = this.root;
        if (pointer == null) {
            this.root = node;
        } else {
            while (pointer != null) {
                if (value < pointer.data) {
                    if (pointer.left == null) {
                        pointer.left = node;
                        pointer = null;
                    } else {
                        pointer = pointer.left;
                    }
                } else {
                    if (pointer.right == null) {
                        pointer.right = node;
                        pointer = null;
                    } else {
                        pointer = pointer.right;
                    }
                }
            }
        }
    }
    length() {
        let lengthToLeft = 0;
        let lengthToRight = 0;
        let pointerToLeft = this.root.left;
        let pointerToRight = this.root.right;
        while (pointerToLeft != null) {
            ++lengthToLeft;
            pointerToLeft = pointerToLeft.left;
        }
        while (pointerToRight != null) {
            ++lengthToRight;
            pointerToRight = pointerToRight.right;
        }
        const length = lengthToRight > lengthToLeft ?
            lengthToRight : lengthToLeft;
        // add 1 for the root
        return length + 1;
    }
}
const tree = new BinaryTree();
tree.add(1);
tree.add(2);
tree.add(3);
console.log("length", tree.length());