how to use js validator with validation errors in codeigniter code example

Example 1: codeigniter form_validation email

$this->form_validation->set_rules('email', 'Email', 'trim|required|valid_email');

Example 2: file form validation codeigniter

if (empty($_FILES['userfile']['name']))
{
    $this->form_validation->set_rules('userfile', 'Image', 'required');
}