How to submit form after validation in jquery

I just try to form submit after validation success. But i have run below code, simultaneously both operations perform same time. I also tried to submit handler method, it gets error only. My code looks like this:

$("#request_form").validate({
        debug: false,
   onfocusout: function(element) {
          $(element).valid();
        },
    errorClass : 'has-error',
    rules: {
      Subject : "required",
      Screen: "required"
    },
    messages: {
      Subject : "Subject cannot be empty",
      Screen: "Screen  cannot be empty"
    },
         submitHandler: function(form) {
        form.submit();
    }
    });



$("#request_form").on('submit',(function(e) 
{
 $("#request_form").validate(); 
 $("#request_form").valid()
 {
  alert("test");
  var action = "Provide_Feedback";
  var form = $('form')[0]; 
  var formData = new FormData(form);

 formData.append('action','Provide_Feedback');
 e.preventDefault();

$.ajax({
    url: "support_update.php", 
    type: "POST",             
    data: formData, 
    contentType: false,      
    cache: false,            
    processData:false,        
    success: function(data)   
    {           
     if (data == "200") {
        alert("Your Request Sent.");
        window.location = 'provide_feedback.php';
        }
        else {  
        alert("There was an error occurred!");
        }                

    }
});

}
}));