undefine variable category

here is my vew code im new in laravel i m not getting what i m doing wrong
please help i tried every thing i m getting undefine variable : category error

<div class="container">
  <h1>category and subcategory</h1>
   <div class="row">
   <div class="col-md-10 col-md-offset-1">
    {!! Form::open(array('url' => '','files'=>true))  !!}
     {!! Form::token(); !!}
    <div class="form-group">
   <label for="">category</label>
   <select class="form-control input-sm" name="" id="">
     @foreach ( $category as $category) 
    <option value=""></option>
        @endforeach
         </select>
          </div>
         <div class="form-group">
        <label for="">subcategory</label>
        <select class="form-control input-sm" name="" id="">
         <option value=""></option>
         </select>
          </div>
           </form>
            </div>
             </div>
           <script type="text/javascript">
         $(document).ready(function() {
         $("#category").on('change',function(e) {
         console.log(e);
         var cat_id = e.target.value; 
        $.get('/ajax-subcat/' + cat_id , function(data){
     //success data
       console.log(data);
            })
       });
     </script>
       </div>    
         </div>
        </div> 

here is my routes

  Route::get('/', function () {
    $category=\App\category::all();
      return view('layouts.app')->with ('category',$category);
      });
  Route::get('/ajax-subcat',function(){
   $cat_id = Input::get('cat_id');
   $subcategory = subcategory::where('category_id', '=', $cat_id)
          ->orderBy('name', 'asc')
          ->get();
     return response()->json($subcategory);
   });

here is error log ErrorException in ec195dc7ec967851481b4815c28c6879244d5d45.php line 87: Undefined variable: category (View: C:\xampp\htdocs\laravel\resources\views\layouts\app.blade.php) (View: C:\xampp\htdocs\laravel\resources\views\layouts\app.blade.php)

is there any way to check flow of data like wise in dot net still getting same error please help and what will cause this type of error

via Bipin Shukla