I have the next trouble. yiiActiveForm('updateMessages', ....) doesn't work, but ajax query is completed and success.

controller.php

 public function actionAjaxValidation()
    {
        \Yii::$app->response->format = Response::FORMAT_JSON;

        $result = [];
        $model = new SomeModelForm();
        $post = \Yii::$app->request->post();
        $model->load($post);

        $result['errors'] = ActiveForm::validate($model);

        return $result;
    }

order of script files in the layout

<script src="/assets/1ac78ba4/jquery.js"></script>
<script src="/js/someModelForm.js"></script>
<script src="/assets/bfc0238/yii.js"></script>
<script src="/assets/bfc0238/yii.activeForm.js"></script>
<script src="/assets/70a7529/js/bootstrap.js"></script>
<script type="text/javascript">jQuery(document).ready(function () {
jQuery('#someModelForm').yiiActiveForm([], []);
});</script>

someModelForm.js

$(function () {
    var $someForm = $(this).find('form'),
        $submitBtn = $someForm.find('[type=submit]'),
        $formData = new FormData($someForm[0]);

    $someForm
        .on('beforeValidate', function () {
            $.ajax({
                url: $someForm.prop('action'),
                data: $formData,
                method: "POST",
                processData: false,
                contentType: false,
                cache: false,
                beforeSend: function () {
                    $submitBtn.button('loading');
                },
                success: function (response) {
                    $someForm.yiiActiveForm('updateMessages', response.errors);
                },
                complete: function () {
                    $submitBtn.button('reset');
                }
            });
        })
        .on('beforeSubmit', function (event) {
            return false;
        });
});

view.html

<?php
/* @var $this yii\web\View
 * @var $model \app\models\SomeModelForm
 */
use yii\widgets\ActiveForm;
$this->registerJsFile('js/someModelForm.js', ['depends' => 'yii\web\JqueryAsset']);
$this->title = 'Some Form';
?>
<div class="site-index">
    <?php $form = ActiveForm::begin([
        'id' => 'someModelForm',
        'enableClientValidation' => false,
        'action' => ['site/ajax-validation'],
        'options' => ['enctype' => 'multipart/form-data']
    ]) ?>
    <?= $form->field($model, 'image')->fileInput([
        'clean' => true,
    ])->label(false) ?>

    <?= \yii\bootstrap\Html::submitButton('Отправить', [
        'class' => 'btn btn-success',
    ]) ?>
    <?php ActiveForm::end() ?>
</div>