Add custom class to the elements of a View

Example:

/**
 * Add classes to a view
 * @param $vars
 */
function MYTHEME_preprocess_views_view_list(&$vars) {
    if ($vars['view']->name == 'article') {
        $view = $vars['view'];
        foreach ($view->result as $row_index => $result) {
            $val1 = strlen($result->field_body[0]['rendered']['#markup']);
            $val2 = strlen($result->field_body[0]['raw']['safe_value']);
                $vars['classes_array'][$row_index] .= ' my-class';
        }
    }
}

Note : Tested in Drupal 7 but not Drupal 8