javascript – Retrieve the id of a select with laravel and ajax-ThrowExceptions

I have two tables: role and persons.

In my persons table I have the foreign key ‘idrole’ of the table: role. I created a drop-down list which retrieves the roles from my table: role

My problem is as follows: I can’t get the id of the selected role from the drop-down list

I am a beginner with laravel and ajax. Thank you for your help

Code of my html page :

<span>Name Role: </span>
<select style="width: 200px" class="namerole" id="nom">

    <option value="0" disabled="true" selected="true">-Select-</option>
    @foreach($roles as $role)
        <option value="{{$role->nom}}">{{$role->nom}}</option>
    @endforeach

</select>

<span>Id Role: </span>
<input type="text" class="idrole" id="idrole" disabled>

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>

<script type="text/javascript">
    $(document).ready(function() {

        $(document).on('change', '.namerole', function () {

            var role_nom = $(this).val();

            var div = $(this).parent();

            $.ajax({
                type: 'get',
                url: '{!!URL::to('findIdRole')!!}',
                data: {'nom':role_nom},
                dataType:'json',
                success: function (data) {
                    console.log('success');
                    div.find('.idrole').val(data.id_r);

                    console.log('error');
                }
            });
        });
    });
</script>

My function:

public function findIdRole(Request $request){
    $rj=DB::table('role')
        ->select('id_r')
        ->where('nom',$request->nom)
        ->first();
    return response()->json($rj);
}

public function findIdRole(Request $request){
    $rj=DB::table('role')
        ->select('id_r')
        ->where('nom',$request->get('nom')) // here is the change
        ->first();
    return response()->json($rj);
}