return object from function is undefined from $.post in jquery

Question

I've a jquery post function that returns a data object from a php code block.

$.post("get_chat_history.php", {
    item_id : item_id,
    participant_1 : participant_1,
    participant_2 : participant_2
}, function(data) {
    alert(data);

    return data;

});

this is called from the following function in another javascript file

var data = getChatHistory(current_member_id,item_global["user"]    ["member_id"],item_global["id"]);
alert(data);

now inside the $.post the alert(data) throws out the correct values in json format, but when I test the same value returned to the calling function I get undefined.

Is there something I'm missing as I want to keep this function generic and callable from elsewhere??

Regards,

Sapatos

Ajax is asynchronous (the A means asynchronous). Why do you think you have to provide a callback? If you could simply return a value, then $.post could return that value directly and you would not need a callback. — Felix Kling
– Felix Kling, Commented Aug 13, 2012 at 11:26
possible duplicate of Javascript Function With JQuery POST Always Returns undefined — Dennis
– Dennis, Commented Aug 13, 2012 at 11:26
Check out the related questions. There are several similar questions which should prove helpful. — Dennis
– Dennis, Commented Aug 13, 2012 at 11:26

Daniil Ryzhkov · Accepted Answer · 2012-08-13 11:26:30Z

1

That's because this function runs asyncronim and returns data to anonymous function function(data) {}. Use callbacks.

Here is example:

function getFoo(callback){
    $.get('somepage.html', function(data){
        callback(data)
    })
}
getFoo(function (data){
     // do something with data
})

answered Aug 13, 2012 at 11:26

Daniil Ryzhkov

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1 Comment

Felix Kling Over a year ago

Or shorter: $.get('somepage.html', callback).

Ohad · Accepted Answer · 2012-08-13 11:30:16Z

0

The problem you are facing is that jQuery.post is asynchronous. When getChatHistory is being called it has not yet received a reply from the server so it is undefined.

For this to work I would implement getChatHistory as a function that takes the data you need to pass to the server, and a function to perform when the 'success' part is triggered.

For more on callbacks.

answered Aug 13, 2012 at 11:30

Ohad

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