Can't call my json function in laravel 4.2 - json

Question

So in my 'edit records' view I have this two dropdrown the first one contains the main category and the second one should contain values based from the main category chosen is the first dropdown. So I implemented an ajax call for this in my view, here is how the dropdown code looks like
<select name="category" id="category" class="dds">
#foreach($mCategories as $lists)
<option value="{{$lists->maincategoryid}}">{{$lists->maincategoryname}}</option>
#endforeach
</select>
<h6>Doc SubClass 1</h6>
<select name="subcategory" id="subcategory" class="dds">
<option value=""></option>
</select>
then I have this in my script to call the ajax function
<script>
$('#category').on('change' , function(e){
console.log(e);
var cat_id = e.target.value;
alert(cat_id);
//ajax
$.getJSON('ajax-subcat?cat_id=' + cat_id , function(data){
console.log(data);
$('#subcategory').empty();
$.each(data, function(index, subcatObj)
{
$('#subcategory').append('<option value="' + subcatObj.Object.subcategoryid +'">' + subcatObj.subcategoryname +'</option>');
});
});
});
</script>
and the code for the ajax call is in my routes and here is how it looks
Route::get('ajax-subcat' ,function()
{
$cat_id = Input::get('cat_id');
$subcategories = DB::table('nsa_subcategory')
->where('maincategoryid' , '=' , $cat_id)
->get();
return Response::json($subcategories);
});
as you can see, in my script I tried to log the data after the $getJSON to check whether or not it went in but I am not getting anything. The thing is I also used this codes in my creating of records so i don't know what my error is now. any ideas? thanks in advance!