The data on the dropdown is not showing

I tried Creating a dependent dropdown to select a city, when I have selected province, the data on the city does not appear.

Province.php

namespace App;
use RajaOngkir;
use Illuminate\Database\Eloquent\Model;
class Province extends Model
{
protected $fillable = ['province_id','name'];
protected $primaryKey = 'province_id';
public static function populate()
{
    foreach(RajaOngkir::Provinsi()->all() as $province) {
        $model = static::firstOrNew(['province_id' => $province['province_id']]);
        $model->name = $province['province'];
        $model->save();
    }
}

}

Regency.php

namespace App;
use RajaOngkir;
use Illuminate\Database\Eloquent\Model;
class Regency extends Model
{
protected $fillable = ['regency_id','province_id','name'];
protected $primaryKey = 'regency_id';
public static function populate()
{
    foreach(RajaOngkir::Kota()->all() as $kota) {
        $model = static::firstOrNew(['regency_id' => $kota['city_id']]);
        $model->province_id = $kota['province_id'];
        $model->name = $kota['type'] . ' ' . $kota['city_name'];
        $model->save();
    }
}

public function province()
{
    return $this->belongsTo('App\Province');
}

}

AddressController.php

namespace App\Http\Controllers;
use App\Http\Controllers\Controller;
use App\Regency;
use Illuminate\Http\Request;
class AddressController extends Controller
{
public function regencies(Request $request)
{
$this->validate($request, [
'province_id' => 'required|exists:provinces,province_id'
]);
    return Regency::where('province_id', $request->get('province_id'))->get();
}

}

_address-field.blade.php

  {!! Form::label('name', 'Nama', ['class' => 'col-md-4 control-label']) !!}
  
    {!! Form::text('name', null, ['class'=>'form-control']) !!}
    {!! $errors->first('name', '
:message
') !!}
  


  {!! Form::label('detail', 'Alamat', ['class' => 'col-md-4 control-label']) !!}
  
    {!! Form::textarea('detail', null, ['class'=>'form-control', 'rows' => 3]) !!}
    {!! $errors->first('detail', '
:message
') !!}
  


  {!! Form::label('province_id', 'Provinsi', ['class' => 'col-md-4 control-label']) !!}
  
    {!! Form::select('province_id', [''=>'']+DB::table('provinces')->lists('name','province_id'), null, ['class'=>'form-control', 'id' => 'province_selector']) !!}
    {!! $errors->first('province_id', '
:message
') !!}
  


  {!! Form::label('regency_id', 'Kabupaten / Kota', ['class' => 'col-md-4 control-label']) !!}
  
    {!! Form::select('regency_id', old('province_id') !== null ? DB::table('regencies')->where('province_id', old('province_id'))->lists('name', 'regency_id') : [], old('regency_id'), ['class'=>'form-control', 'id' => 'regency_selector']) !!}
    {!! $errors->first('regency_id', '
:message
') !!}
  


  {!! Form::label('phone', 'Telepon', ['class' => 'col-md-4 control-label']) !!}
  
    
      +62
      {!! Form::text('phone', null, ['class'=>'form-control']) !!}
    
    {!! $errors->first('phone', '
:message
') !!}