//...
use App\Models\Employee;
//...
    public function update($id) {
        $employee = Employee::find($id);
        $employee->name = request()->get('name');
        $employee->city = request()->get('city');
        $employee->salary = request()->get('salary');
        $res = $employee->save();

        response()->json([
            'success' => $res
        ]);        
    }