我嘗試從數(shù)據(jù)屬性獲取值并傳遞給Java腳本變量，但它給出了未定義的值    $(document).on("click","#edit_cust",function(){        var customer_id=$(this).data("id");        var customer_name=$(this).data("name");        var customer_phone=$(this).data("phone");        var customer_addr=$(this).data("mail");        var customer_mail=$(this).data("phone");       });<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script><div class='btn-group' role='group' >     <a id="edit_cust" data-target="#edit" data-toggle="modal"><button      type='button' class='btn btn-primary btn-sm' data-id="<?php echo      $customer["cus_id"]; ?>" data-name="<?php echo $customer["cus_name"]; ?>"      data-phone="<?php echo $customer["cus_phone"]; ?>" data-addr="<?php echo      $customer["cus_address"]; ?>" data-mail="<?php echo $customer["cus_mail"]; ?      >"><span class="fas fa-user-edit edit_data" aria-hidden='true'></span>      </button></a>    </div>