yii\validators\FilterValidator::clientValidateAttribute PHP Method

    public function clientValidateAttribute($model, $attribute, $view)
    {
        if ($this->filter !== 'trim') {
            return null;
        }
        $options = [];
        if ($this->skipOnEmpty) {
            $options['skipOnEmpty'] = 1;
        }
        ValidationAsset::register($view);
        return 'value = yii.validation.trim($form, attribute, ' . json_encode($options, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE) . ');';
    }