JAVASCRIPT

sum all odd in binary search tree recursion javascript

function sumOfAllOdd(BT) {
    if (BT.isEmpty()) return 'empty BT';
    function _sumOdd(node, sum = 0) {
        if (node === null) {
            return 0;
        } else {
            if (node.value % 2 != 0) {
                sum += node.value;
            }
        }
        return sum + _sumOdd(node.left) + _sumOdd(node.right);
    }
    return _sumOdd(BT.root);
}