Ideal way to use ajax in laravel

I want to save the user data in users table using AJAX.when i check the post route in postman It throws TokenMismatchException in VerifyCsrfToken.php line 67: . I have added the following code in the head.blade <meta name="csrf-token" content="{{ csrf_token() }}">

$(document).ready(function()
{
    $('.sendBtn').click(function()
    {
      var _token = $('input[name="_token"]').val();
      var customerName = $('.customerName').text();
      var url='{{ url('postitemdata') }}';
          $.ajax
          ({
            url: url,
            data: {           
       'username':customerName,
            '_token': _token
              },
            type: 'POST',
            success: function(data)
            {
              $('#loadingmessage').hide();
            }
          });
    });
});

in controller

    public function postitemdata()
    {
        if(Request::ajax())
        {
        $users= new User(Input::all());
                 $users->save();
               return redirect()->back()->with('success','data added Successfully');
    }
    }

In view

<form class="form-horizontal" role="form" enctype="multipart/form-data" method="POST" action="{{ url('postitemdata') }}">
<span class="customerName ">yyy</span>
</form>