How to Send FormData from AJAX and Jquery

$("form#frm").submit(function(event){

      event.preventDefault();

     
       //var formData = $('.frm_coupon').serialize(); 

      var formData = new FormData($(this)[0]);

        

      $.ajax({

                   url:'index.php?ajax',

                   processData: false,

                   contentType: false,

                   type: "POST",

                  data:formData,

                  success:function(res){

                            console.log(res);

                  }

              });

            return false;

    });