Connect an Ionic3 test app with laravel 5.4 API data - laravel

Question

Now I try to connect an Ionic3 test app with laravel 5.4 API data.
Ionic code is click here
So, my goal is to show list page in Ionic3 app.
But there are nothing to show.
Could you some advice where I modify code?
Thank you in advence.
Laravel 5.4 API
namespace App\Http\Controllers;
use App\Customer;
use Illuminate\Http\Request;
class CustomerController extends Controller
{
public function index()
{
$customer = Customer::all();
return response()->json($customer);
}
public function store(Request $request)
{
$this->validate($request, [
'name'=>'required',
'email' =>'required',
'tel' =>'required',
]);
$customer = Customer::create($request->all());
return response()->json($customer);
}
public function show($id)
{
$customer = Customer::find($id);
return response()->json($customer);
}
public function update(Request $request, $id)
{
$customer = new Customer;
$customer->name = $request->input('name');
$customer->email = $request->input('email');
$customer->tel = $request->input('tel');
$customer->address = $request->input('address');
$customer->note = $request->input('note');
$customer->save();
return response()->json($customer);
}
public function destroy($id)
{
$customer = Customer::find($id);
$customer->delete();
return response()->json($customer);
}
}