Javascript ajax returns undefined

Question

This functions always returns undefined but the alert is showing the right value.

    function _gesamt()
{
   var link = "speichern.php?gesamt=true";
    //alert(link);
    var req = new XMLHttpRequest();
    req.onreadystatechange = function(){
        //alert("Ready:"+req.readyState);
        if(req.readyState == 4){
            alert(req.responseText);
            return req.responseText;
        }
    }
    req.open("GET",link,false);
    req.send();
}

Yet another duplicate (among hundreds) of [How to return AJAX response Text?](http://stackoverflow.com/questions/1225667/how-to-return-ajax-response-text) — Quentin, Sep 06 '13 at 12:12
But if I change the false to true it still returns undefined.. — Liam Schnell, Sep 06 '13 at 12:12
`function _gesamt` doesn't have a return statement so it will always return `undefined`, but see the duplicate for the right way to handle this. — Quentin, Sep 06 '13 at 12:14

score 1 · Answer 1 · answered Sep 06 '13 at 12:17

1

AJAX is asynchronous. So you must use callbacks.

function _gesamt(callback)
{
   var link = "speichern.php?gesamt=true";
    //alert(link);
    var req = new XMLHttpRequest();
    req.onreadystatechange = function(){
        //alert("Ready:"+req.readyState);
        if(req.readyState == 4){
            callback(req.responseText);
        }
    }
    req.open("GET",link,false);
    req.send();
}

_gesamt(function(response) {
    // do your work here
    alert(response);
});

answered Sep 06 '13 at 12:17

Murat Çorlu

8,207
5
53
78

Well, If I just c/p it it is still not running properly. Here is the rest of the code [code]_bp_iframe.default_amount = _gesamt(); /* Donation-amount, integer 1-99 */ [/code] – Liam Schnell Sep 06 '13 at 12:21

score 0 · Answer 2 · answered Sep 06 '13 at 12:15

0

The return is inside the inner function, so running _gesamt is not supposed to return anything (even setting aside the question of why you would want to issue AJAX requests this way)

answered Sep 06 '13 at 12:15

alexsh

1,121
8
12

Javascript ajax returns undefined

2 Answers2