I believe that if you put your logic in a controller you would be better off instead of trying to put the logic in a route. I know for json to work I had to put this use statement at top of controller:

use Illuminate\Contracts\Routing\ResponseFactory;

and method looks like:

public function jsontest(ResponseFactory $response) {
            $dummy = $_GET['id'];
            $mydata = \Illuminate\Support\Facades\DB::table('powners')
                    ->where('oname', 'like', 'D%')
                    ->orderBy('oname', 'asc')->get();
            return $response->json($mydata);        
           
            
        }

Notice the ResponseFactory $response part.
Sorry I do not know how or would I ever cram code into a route. I try to use clean routes like:

Route::get('tryjson', array('uses' => 'PownersController@jsontest'));

my json post request has a data key named "id", now how im going to pass it from routes to my controller?

my json post request

$.post("/employees", {id:"1"}, function(response){
    if(response.success)
    {
        var branchName = $('#branchname').empty();
        $.each(response.employees, function(){
            $('<option/>', {
                value:$(this).user_no,
                text:$(this).firstname
            }).appendTo(branchName);
        });
    }
}, 'json');

as you can see from my json post request i have put a key value name id

my routes

Route::post('employees', [
    'as' => 'employees', 'uses' => 'mot@getemployee'
]);

and my controller

public function getemployee($id){
            $employees = employees::where("branch_no", $id)->lists('firstname', 'user_no');
            return response()->json(['success' => true, 'employees' => $employees]);
}

as you can see, I have an argument $id, it supposedly, its where the key value named id from the json post request will be put and be used from the query stuff.

Assuming you use Laravel 5

Route::post('employees/{id}', [
    'as' => 'employees', 'uses' => 'mot@getemployee'
]);