Send data per Ajax to Controller in Laravel 5.8 - ajax

Question

I have the Ajax request
Here is the code of script
<script>
$('#variant_model').change(function(){
var value = $('select#variant_model').val();
$.ajaxSetup({
headers: {
'X-CSRF-TOKEN': $('meta[name="csrf-token"]').attr('content')
}
});
$.ajax({
type:"POST",
url: "showVariantModel",
data: value,
success: function(data){
alert(data);
}
})
});
</script>
When I put in my web.php the code
Route::post('/showVariantModel', function(){
if(Request::ajax()){
return var_dump(Response::json(Request::all()));
}
});
Everything looks fine and I receive the response in my alert.
But when I want to put everything into controller I receive the error 500 in the console
Below I will add my code from my web.php and Controller.
Framework is Laravel 5.8
//web.php
Route::post('/showVariantModel', 'VariantsController#checkAttribute');
//VariantsController.php
public function checkAttribute()
{
if(Request::ajax()){
return var_dump(Response::json(Request::all()));
}
Who knows what am I doing incorrect, please give an advice...
Updating the error
https://i.stack.imgur.com/iDvvG.jpg
Thank's Md.Sukel Ali I updated my controller. Not it looks
<?php
namespace App\Http\Controllers;
use Illuminate\Http\Request;
use App\Variants;
class VariantsController extends Controller
{
public function checkAttribute(Request $request)
{
if($request->ajax()){
return response()->json($request->all());
}
}
}
Everything works fine now.
Thank you.

Answer 1

The closing tag is missing
public function checkAttribute()
{
if(Request::ajax()){
return Response::json(Request::all());
}
}

Answer 2

Instead of blinding guess what happening under the hood of ajax call. I suggest you to learn how to debug ajax request.
Go to your browser right click and Inspect then go to Network tab then you can see your request. Click on your request then look for response tab. There you can find exactly what happened.
public function checkAttribute(Request $request)
{
if($request->ajax())
{
return response()->json($request->all());
}
}

Answer 3

You need to add imports in your controller:
use Illuminate/Http/Request;
use Illuminate/Http/Response;