如何解决我的动态下拉菜单。它不会启动

Question

我正在为我的搜索项目的国家/地区城市实现动态下拉选择。我在运行代码方面遇到困难。我只会得到错误。

我有一些用于Controller，Java和HTML代码的代码。从数据库加载国家（地区）工作正常，但不会加载一个国家拥有的城市。

型号

    namespace App;
    use App\Listings;
    use Illuminate\Database\Eloquent\Model;

    class Cities extends Model
    {
        protected $table = 'newcitymun';
        protected $fillable = ['citymunDesc'];
        public $timestamps = false;
        public static function getCitymunInfo($id) 
        { 
            return Citymun::find($id);
        }
    }

控制器

    namespace App;
    use Illuminate\Database\Eloquent\Model;
    class Location extends Model
    {
        protected $table = 'location';
        protected $fillable = ['location_name'];
        public $timestamps = false;  
    }

索引

    <select id="location" name="location" class="form-control">
        <option value="">{{ __('messages.select_location') }}</option>
        @foreach(\App\Location::orderBy('location_name')->get() as $location) 
            <option value="{{$location->id}}">{{$location->location_name}}</option> 
        @endforeach 
    </select>


    <select id="citymun" name="citymun" class="form-control">
        <option value="">{{ __('messages.select_location') }}</option>
        @foreach(\App\Citymun::orderBy('citymunDesc')->get() as $citymun) 
        <option value="{{$citymun->id}}">{{$citymun->citymunDesc}}</option> 
        @endforeach 
    </select>

JavaScript

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

        $("#location").change(function(){
          var loc=$("#location").val();
        $.ajax({
          type: "GET",
        url: "{{ URL::to('ajax_citymun') }}/"+loc,

        success: function(result){

        $("#citymun").html(result);
           }
        });                
        });
    });
    </script> 

citymun php

    <option value="">.. select city ..</option>
    @foreach($citymun as $i => $citymun)                                  
      <option value="{{$citymun->id}}">{{$citymun->citymunDesc}}</option>                                                  
    @endforeach