How to do a synchronous json ajax call with jquery

Question

I have the following json ajax call:

$.getJSON(server_data.secure_api+'/e/account/check/?callback=?', queryData,
    function(data) {
        has_error = (data.status == 'failure');
});

Which works perfectly, except that it is asynchronous. I now need to make it synchronous, because I need to pause the calling function until has_error is set. How do I do this?

I have already tried using a .ajax call, like this:

jQuery.ajax({
    url:        server_data.secure_api+'/e/account/check/?callback=?',
    data:       queryData,
    DataType:   'jsonp',
    success:    function(result) {
                has_error = (data.status == 'failure');
            },
    async:      false
});

But it doesn't work! I've tried setting the DataType to json, jsonp, or not set; I've tried including the ?callback=? and I've tried leaving it off; none of this has worked. What am I doing wrong?

Solution

By default, all requests are sent asynchronously (i.e. this is set to true by default). If you need synchronous requests, set this option to false. Cross-domain requests and dataType: "jsonp" requests do not support synchronous operation. Note that synchronous requests may temporarily lock the browser, disabling any actions while the request is active.

As of jQuery 1.8, the use of async: false with jqXHR ($.Deferred) is deprecated; you must use the success/error/complete callback options instead of the corresponding method

http://api.jquery.com/jQuery.ajax/

Comments

[Benubird]

This is happening as part of a form submit, which aborts if has_error. I could do it that way, but this would be tidier.

[Benubird]

So, are you saying that synchronous calls are no longer possible?

[Jay Blanchard]

That's pretty much what he is saying.

[rookie]

If you're using AJAX why are you trying to do a standard form submit? Why not use AJAX for everything?

[Benubird]

Because I need to submit the data to another page, and doing an ajax request to save it followed by a redirect seems wasteful.

[rookie]

Well those really are your only two legitimate options. Place the form submission inside the AJAX callback or avoid using a form submission at all.

[rookie]

@Benubird - For future reference, just because someone is telling you something you don't want to hear is no reason not to give an up vote.

[Benubird]

You haven't told me anything useful - what callback function? where? how do I place code in it? I guess you are probably talking about jquery.deferred, but you haven't named it here. I can't give someone an upvote for saying RTFM, when they don't even link me to the manual in question. Upvotes are for useful answers; this answer is not useful to me.

[rookie]

It is useful you just lack the knowledge to apply it. Which is fine but you could specify which option you are interested in learning more about and I'd be happy to extrapolate. Nowhere in my post did I say or imply "RTFM". You came up with that all on your own.

[Stijn de Witt]

@SpencerRuport I'm getting the same vibe from it though... -1

[rookie]

@StijndeWitt - What part of "specify which option you are interested in learning more about and I'd be happy to extrapolate" gives you a RTFM vibe?