jQuery AJAX request returns object - php

Question

I have the following AJAX request:
$(function(){
$("#MPrzezn").typeahead({
hint: true,
highlight: true,
minLength: 3
},
{
name: 'test',
displayKey: 'value',
source: function(query, process){
$.ajax({
url: 'sprawdzKraj.php',
type: 'POST',
data: 'query=' + query,
dataType: 'JSON',
async: true,
success: function(data){
process(data);
console.log(data);
}
});
}
});
});
... and the following php on backend:
<?php
require_once 'core/init.php';
$user = new User(); //current User
if($user->isLoggedIn()){
if(isset($_POST['query'])){
$query = $_POST['query'];
$delegacja = new Delegacja();
$dataListaDelegacji = $delegacja->listujMiasta($query);
header('Content-Type: application/json');
$json_response = json_encode($dataListaDelegacji);
echo $json_response;
}
} else {
$isLoggedIn = false;
$smarty->assign("userid","",true);
$smarty->assign("isLoggedIn",$isLoggedIn,true);
Redirect::to('login.php');
}
The php script returns a proper json:
[{"ID":"66","IDKraju":"117","NazwaMiasta":"Inowroc\u0142aw","MiastoTlumaczenie1":null,"MiastoTlumaczenie2":null},
{"ID":"251","IDKraju":"117","NazwaMiasta":"\u015awinouj\u015bcie","MiastoTlumaczenie1":null,"MiastoTlumaczenie2":null},
{"ID":"2222","IDKraju":"74","NazwaMiasta":"Rhinow","MiastoTlumaczenie1":null,"MiastoTlumaczenie2":null},
{"ID":"3508","IDKraju":"94","NazwaMiasta":"San Bernardino","MiastoTlumaczenie1":null,"MiastoTlumaczenie2":null}]
The picture below shows how the json is being picked up by browser:
There are 4 cities that match the query - each object is a city entry
My goal is to pass values of "NazwaMiasta" to a typeahead input, but I get "undefined" entries. I tried different things but it always keeps showing undefined like this:
Red arrows show all 4 json nodes
I hope I described my problem well. I understand that I'm pretty close, but I cannot find the solution myself. I'll appreciate any help.
Thanks

Answer 1

You have to put right displayKey value!
insted of :
displayKey: 'value',
set :
displayKey: 'NazwaMiasta',
EDIT :
Detailed explanation : When you return data via ajax call, typeahead doesn't know what value to display. So you must set where is value for that key. Your return array of object that have structure like this :
['key1':'value1', 'key2':'value2',...]
By setting ie 'key1' , typeahead knows how to access value ie :
currentElement['key1']...
and than put that value to html.