Как получить имя класса с родительской функцией в jquery

function addIncludeTextBox(obj){
  console.info($(obj).closest('[class^=field_wrapper]').attr("class"))
}

<script src = "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div class = "field_wrapper_1">
        <span class = "error php-error" id = "php-error_includes" style = "display: none"></span> 
    <div class = "row">
        <div class = "col-md-11">
            <div class = "form_group">
                <label class = "form_label">Includes <span>*</span></label>
                <input class = "form_input" name = "includes[][]" id = "includes" placeholder = "Enter the details of fees includes" type = "text">                                    

            </div>
        </div>
        <div style = "padding-top: 3.6%;" class = "col-md-1">
            <a href = "javascript:void(0);" class = "add_button" onclick = "addIncludeTextBox(this)" title = "Add field"><i class = "fa fa-plus" aria-hidden = "true">+</i></a>
        </div>
    </div>
</div>