double insert in database while submiting form using Ajax in laravel - ajax

Question

I'm trying to submit my form with ajax.
So I'm using the following ajax code:
<script>
if ($("#castingform").length > 0) {
$("#castingform").validate({
rules: {
casting_name: {
required: true,
maxlength: 50
},
casting_photo: {
required: true
},
},
messages: {
casting_name: {
required: "Please enter name",
maxlength: "Name should be 50 characters long."
},
casting_photo: {
required: "Please enter photo"
},
},
submitHandler: function(form) {
$.ajaxSetup({
headers: {
'X-CSRF-TOKEN': $('meta[name="csrf-token"]').attr('content')
}
});
$('#castingform').on('submit', function(event) {
event.preventDefault();
$.ajax({
url:"{{ url('castings') }}",
method:"POST",
data:new FormData(this),
dataType:'JSON',
contentType: false,
cache: false,
processData: false,
success:function(res) {
$("#createBtn").removeClass("disabled");
$("#createBtn").text("Sign in");
if (res.status == "success") {
$(".result").html("<div class='alert alert-success rounded'><button type='button' class='close' data-dismiss='alert'>×</button>" + res.message+ "</div>");
/* location.reload();*/
} else if(res.status == "failed") {
$(".result").html("<div class='alert alert-danger alert-dismissible'><button type='button' class='close' data-dismiss='alert'>×</button>" + res.message+ "</div>");
}
}
});
});
}
})
}
</script>
But when I click for the first time on the button submit, the success message doesn't show, and for the second time I get the success message but I find a double insert in the database.
My Controller
EDIT
public function store(Request $request)
{
$validator = Validator::make($request->all(), [
'casting_name' => 'required',
'casting_photo' => 'required|image|mimes:jpeg,png,jpg,gif,svg|max:2048',
]);
if ($validator->passes()) {
$input['casting_photo'] = time().'.'.$request->casting_photo->extension();
$request->casting_photo->move(public_path('castingimages'), $input['casting_photo']);
$data = [
'casting_name' => $request->casting_name,
'casting_photo'=> $input['casting_photo']
];
Casting::create($data);
return response()->json([
"status" => "success",
"message" => "Success! post created."
]);
}
return response()->json([
"status" => "failed",
"message" => "Alert! post not created"
]);
}
I think the problem is in this line submitHandler: function(form) and this line $('#castingform').on('submit', function(event) {, but I don't know how to solve it.