1

I got this code:

function server_request(module,section,action,data) {
    data['module'] = module;
    data['section'] = section;
    data['action'] = action;
    var responsetxt = null;
    $.post('../application/server.php', data, function(data) {
        responsetxt = data;
    });
    return responsetxt;
}

And it return's null ?

What i want is let the server_request function return the responseText? But at some way it doesn't work, why? And how to let it work?

seymar
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    See http://stackoverflow.com/questions/133310/how-can-i-get-jquery-to-perform-a-synchronous-rather-than-asynchronous-ajax-req – Roatin Marth Nov 10 '10 at 18:04
  • This question gets asked *all the time*. It appears to be a fundamental stumbling block in learning how asynchronous Javascript works. – Pointy Nov 10 '10 at 18:23

2 Answers2

5

You're providing a callback function to $.post, which will be run when the request is returned. The server_request function returns immediately (i.e. before the response is available) so responsetxt will still be null.

To get around this you could add a callback parameter to server_request, then execute it in the anonymous function you provide to the $.post call:

function server_request(module,section,action,data,callback) {
    data['module'] = module;
    data['section'] = section;
    data['action'] = action;
    $.post('../application/server.php', data, function(data) {
        callback(data);
    });
}

You could then use this like:

$(function() {
    var module = x, section = y, data = z;
    server_request(module, section, data, function(response) {
        $('#result').html(response); // do stuff with your response
    });
});

Check out continuation passing style for more information ( http://en.wikipedia.org/wiki/Continuation-passing_style and http://matt.might.net/articles/by-example-continuation-passing-style/).

HarryM
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  • Nah, I don't want functions etc. outside the `server_request` function, I realy need to let the `server_request` function return the response, but how... – seymar Nov 10 '10 at 18:04
  • or even `$.post('../application/server.php', data, callback)` – Drew LeSueur Nov 10 '10 at 18:04
  • ROFL, you beat me, I was posting while you posted this, sorry for the duplicate. – Ben Lesh Nov 10 '10 at 18:05
  • @Stijntjhe: You're going to have to use functions, that's the name of the game nowadays in javascript, especially with these post/ajax/html type calls. – Ben Lesh Nov 10 '10 at 18:07
  • Stijntjhe: you could make the request blocking by specifying 'async: false' but that's not recommended as it'll lock up the browser. Beyond this it isn't really possible to return the result from that function - it's just something you have to deal with when using AJAX. – HarryM Nov 10 '10 at 18:08
  • Deleted my answer as it was a duplicate. +1 for this one. – Ben Lesh Nov 10 '10 at 18:08
  • The `$.post()` function returns an `XMLHttpRequest` with `responseText` set? :D But when I call that variable like `console.log($.post(blabla).responseText);` it logs nothing, weird. – seymar Nov 10 '10 at 18:11
3

You could get the return value, but only when doing a synchronous call instead of an asynchronous one:

function server_request(module,section,action,data,callback) {
    data['module'] = module;
    data['section'] = section;
    data['action'] = action;
    responsetxt = $.ajax({
       "url": '../application/server.php', 
       "async": false,
       "type": "POST",
       "data": data
       }).responseText;
    return responsetxt;

}

Remember that a synchronous call like this freezes the browser until the server responds.

user546153
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