I have created a content type "Type A" and added three fields to content type. I want to display value in third field equal to (value of first field - value of second field).

I want to implement the same using ajax functionality. I have created a custom module and alter the "node form" and add ajax to field 1 but ajax is not working on change event of textfield.

Code Snippet:

function employee_login_form_alter(&$form, &$form_state, $form_id){

    $form['field_total_value']['#prefix'] = '<div id="calculate-total-value">';
    $form['field_total_value']['#suffix'] = '</div>';
    
    
    $form['field_value_first']['#ajax'] = array(
        'callback' => 'employee_login_ajax',
        'wrapper' => 'calculate-total-value',
        'method' => 'replace',
        'event' => 'change',    
    );
    
    $form['field_value_first']['und'][0]['#ajax'] = array(
        'callback' => 'employee_login_ajax',
        'wrapper' => 'calculate-total-value',
        'method' => 'replace',  
        'event' => 'change',        
    );

}

function employee_login_ajax(&$form, &$form_state) { //print_r($form); exit;
  print_r($form_state['values']);
}

Thanks in advance.

I have created a content type "Type A" and added three fields to content type. I want to display value in third field equal to (value of first field - value of second field).

I want to implement the same using ajax functionality. I have created a custom module and alter the "node form" and add ajax to field 1 but ajax is not working on change event of textfield.

Code Snippet:

function employee_login_form_alter(&$form, &$form_state, $form_id){

    $form['field_total_value']['#prefix'] = '<div id="calculate-total-value">';
    $form['field_total_value']['#suffix'] = '</div>';
    
    
    $form['field_value_first']['#ajax'] = array(
        'callback' => 'employee_login_ajax',
        'wrapper' => 'calculate-total-value',
        'method' => 'replace',
        'event' => 'change',    
    );
    
    $form['field_value_first']['und'][0]['#ajax'] = array(
        'callback' => 'employee_login_ajax',
        'wrapper' => 'calculate-total-value',
        'method' => 'replace',  
        'event' => 'change',        
    );

}

function employee_login_ajax(&$form, &$form_state) { //print_r($form); exit;
  print_r($form_state['values']);
}