undefined error when iterating over json list

Question

i got this code that keep on returning undefined msg instead of the expected html. Purpose of function: the purpose of the below function is to return notifications in away similar to fb one's. the code is working fine. but there's something wrong with the getJSON part that i couldn't figure out. so instead of returning "clonex1 likes your post" i get undefined. the code

function buzzme()
{
jQuery('#cnumber').removeClass();
jQuery('#cnumber').empty();

jQuery('#floating_box').toggle();

 var nHeader = '<div id="floating_box" class="fb">' +
'<div id="header"><span id="htext">Notifications</span></div>' +
'<div id="int">' +
'<div id="bodyx">' +
'<ul>';
var nFooter = '</ul>' +
'<div class="jfooter">' +
'<a href="#" id="seemore">See all notifications</a>' +
'</div>' +
'</div>' +
'</div>' +
'</div>';
var nContent;

jQuery.getJSON('notifications.php', {'n':1,'dht':3692}, function(response){
    jQuery.each(response, function(i, nt2){
        nContent += '<a href="#"><li id="lix">sdfsdfsd'+nt2.img+' '+nt2.notifier+'</li></a>';

    })

});

alert(nContent);
var nFinal = nHeader+nContent+nFooter;
if (!jQuery('#floating_box').length) {
  jQuery('body').append(nFinal);
}
}

notifications.php - setUpFlayout(); and setUpJSONList()

    function setUpFlyout() {
    $notify = new se_notify();
    $data2 = $notify->notify_summary();
    $trk = 0;

    if($data2['total'] >= 1) {
    for($i = 0; $ $i <= $data2['total']; $i++) {
$nid = $data2['notifys'][$i]['notify_id'];
$im = $data2['notifys'][$i]['notify_icon'];
$img = "<img src='./images/icons/$im' />";
$notifier = $data2['notifys'][$i]['notify_text'][0];
$atype = $data2['notifys'][$i]['notifytype_id'];
$url = '';
$url2 = $data2['notifys'][$i]['notify_url'];
if($atype == 1) {
  $url = ' has sent you friend <a href='.$url2.'>request</a>';  
}
$trk++;    
if($data2['total'] >= 2) {
    $ret_arr = '';
     if($i == 0) {
         $ret_arr = '[';
     }
     $ret_arr = $ret_arr.setUpJSONList($data2['total'], $nid, $img, $notifier, $url, $trk);
     if($i == $data2['total']-1) {
         $ret_arr = $ret_arr.']';
     }
    echo ''; 
} else if($data2['total'] == 1){
   //$ret_arr = '[{"dh3":"'.$data2['total'].'","nid":"'.$nid.'", "img":"'.$img.'","notifier":"'.$notifier.'","url":"'.$url.'"}]';
   $ret_arr = '';
   echo $ret_arr;
}
    if($i == ($data2['total']-1))
        break;
        }
    }
}

setUpJSONList();

function setUpJSONList($total, $nid, $img, $notifier, $url, $track) {
    $comma = ',';
    $lp = '';
    $rp = ']';
    $result = '';
    if($track == $total) {
    $result = '{"pos":"'.$track.'","dh3":"'.$total.'","nid":"'.$nid.'","img":"'.$img.'","notifier":"'.$notifier.'", "url":"'.$url.'"}';
    } else {
        $result = '{"pos":"'.$track.'","dh3":"'.$total.'","nid":"'.$nid.'","img":"'.$img.'","notifier":"'.$notifier.'", "url":"'.$url.'"},';    
    }
    return $result;
}

thanks

i edited the post including functions involved setUpJSONList() and setUpFlayout() — clonex1
– clonex1, Commented Aug 1, 2010 at 13:47
the json output is tested against JSONlint result was valid. something wrong on the js side that i couldn't figure it out — clonex1
– clonex1, Commented Aug 1, 2010 at 13:49

Marimuthu Madasamy · Accepted Answer · 2010-08-01 14:07:32Z

3

Your usage of nContent after getJSON might be undefined since getJSON is asynchronous and would not have completed initializing nContent. You need to move the code using nContent inside the callback of getJSON.

jQuery.getJSON('notifications.php', {'n':1,'dht':3692}, function(response){
    jQuery.each(response, function(i, nt2){
        nContent += '<a href="#"><li id="lix">sdfsdfsd'+nt2.img+' '+nt2.notifier+'</li></a>';

    })
    alert(nContent);
var nFinal = nHeader+nContent+nFooter;
if (!jQuery('#floating_box').length) {
  jQuery('body').append(nFinal);
}
});

edited Aug 1, 2010 at 14:07

answered Aug 1, 2010 at 13:51

Marimuthu Madasamy

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4 Comments

Nick Craver Over a year ago

+1 - This is correct, it's not a "might be" either, it's guaranteed to be undefined at the point it's being used (single-threading and such).

clonex1 Over a year ago

am sorry for this am kinda fuzzy. can you demo that in a snippet?

clonex1 Over a year ago

Thanks Marimuthu, that worked but its still showing undefined. here's screenshot hinuts.com/yt5.PNG

Marimuthu Madasamy Over a year ago

Screenshot is not opening for me. But I guess since nContent is initially undefined and you are appending strings to it, initial undefined is converted to string and precedes your string. Have var nContent = ''; //initialize with blank string

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