Can't save information from getJSON into var

Question

Could anyone explain to me why the following is happening. First of all see my code below. Trying to get data via a JSON request and save it for later use.

        var entities;

        //@jsonGetEntities is an url build by asp.net MVC and this works
        $.getJSON("@jsonGetEntities", function(getdata) {
            entities = getdata;

            //I would expect that this is the first alert
            alert(entities + "first");
        });            

        //I would expect that this is the second alert
        alert(entities + "second");

However, the alert that I would expect to be first comes second and entities is actually filled.

In the last alert entities is not filled.

I can't seem to understand why my json is not saved to the var and why an alert that is called later is executed earlier? Could you also give me a possible other solution?

Yet another duplicate of [How to return AJAX response Text?](http://stackoverflow.com/questions/1225667/how-to-return-ajax-response-text) — Quentin, May 22 '13 at 13:07
I don't see how this is a duplicate, I don't even use prototype. Thanks for the tip though. The answers there can come in handy. — Nick N., May 22 '13 at 13:12
It's Ajax. The problem is the same. The solution is the same. The syntax is very slightly different. — Quentin, May 22 '13 at 13:12

techfoobar · Accepted Answer · 2013-05-22T13:19:49.467

3

That is because getJSON() is asynchronous.

The first alert is inside the success callback of getJSON which gets executed asynchronously once the server returns.

The second alert however, runs immediately after triggering the AJAX request (via getJSON())

edited May 22 '13 at 13:19

answered May 22 '13 at 13:06

techfoobar

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Ok fair enough, can I force it to wait somehow? – Nick N. May 22 '13 at 13:07
2

Well, you can. But you shouldn't. – techfoobar May 22 '13 at 13:08
@NickN. make an ajax request and set async false – Sam May 22 '13 at 13:08
but how can I use the data got with `getJSON` later? – Nick N. May 22 '13 at 13:08
@NickN. Please see the following references: [jQuery Deferred Object](http://api.jquery.com/category/deferred-object/) and [jQuery Callbacks](http://api.jquery.com/jQuery.Callbacks/). These may be able to help you. – War10ck May 22 '13 at 13:09
For the best user experience, I advice you to read the above links (posted by War10ck) and then design your application around callbacks. – techfoobar May 22 '13 at 13:10
I can't seem to get it working with my syntax, should I use another? – Nick N. May 22 '13 at 13:16

score 0 · Answer 2 · answered May 22 '13 at 13:09

0

 $.getJSON("@jsonGetEntities", function(getdata) {
            entities = getdata;

            //I would expect that this is the first alert
            alert(entities + "first");
            setTimeout(function() {
               //I would expect that this is the second alert
               alert(entities + "second");
            },2000); // wait 2 sec.
        });

answered May 22 '13 at 13:09

Raf A.

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Why would you wait to execute the second alert? – War10ck May 22 '13 at 13:09
And how can you be sure it'll be done in 2000 ms! And why is the second alert inside the callback? The whole point was about how he can use it *outside*.. – techfoobar May 22 '13 at 13:11
This answer doesn't make any sense, I am not going to wait for a random number of seconds. That doesn't seem like a clean solution. Thanks though. – Nick N. May 22 '13 at 13:15

Can't save information from getJSON into var

2 Answers2