I have a registration form :

<div class="register-error" id="register-error">{{ form.status_messages_user_register_form }}</div>  <div class="row">  <div class="col-sm-6">{{ form.field_first_name }}</div>  <div class="col-sm-6">{{ form.field_last_name }}</div></div>  <div class="clear"></div> {{ form.account.mail }} {{ form.account.name }} <div class="row"> <div class="col-sm-6">{{ form.account.pass.pass1 }}</div> <div class="col-sm-6">{{ form.account.pass.pass2 }}</div></div> <div class="clear"></div> {{ form.form_build_id }} {# required #} {{ form.form_token }}{# required #} {{ form.form_id }} {# required #} {{ form.actions }} 

Now i want to add custom validation for the registration.I have a custom ajax handler for registration using form alter:

$form['actions']['submit']['#ajax']  = [          'callback'    => 'custom_register_form_ajax_validate',          'event'       => 'click',          '#attributes' => [            'class' => [              'use-ajax',           ],          ],        ];        $form['#attached']['library'][]      = 'core/drupal.dialog.ajax';        $form['#attached']['library'][]      = 'core/drupal.ajax';         $form['#prefix']                     = '<div id="email-valid"></div>'; 

And this is my function :

function custom_register_form_ajax_validate(&$form, $form_state){  $response = new AjaxResponse();    $form_state->setTemporaryValue('entity_validated', TRUE);    $firstname = $form['field_first_name']['widget']['#default_value'];    $email = $form_state->getValue('mail');    $pass1 = $form_state->getValue('pass1');    $pass2 = $form_state->getValue('pass2');      if($firstname == ''){          $text = '<h5 style="color:red;">Firstname is required.</h5>';           $response->addCommand(new InvokeCommand('.form-text', 'css', array('border-bottom', '2px solid red')));       $response->addCommand(new HtmlCommand('#email-valid', $text));     }     if($lastname == ''){          $text = '<h5 style="color:red;">Lastname is required.</h5>';           $response->addCommand(new InvokeCommand('.form-email', 'css', array('border-bottom', '2px solid red')));       $response->addCommand(new HtmlCommand('#email-valid', $text));     }     if($email == ''){          $text = '<h5 style="color:red;">Email field is required.</h5>';           $response->addCommand(new InvokeCommand('.form-email', 'css', array('border-bottom', '2px solid red')));           $response->addCommand(new HtmlCommand('#email-valid', $text));     } } 

I want to validate “Firstname is required” condition.But when i submit and validate the form,always showing “Email field is required”.

How can i solve this issue?