Search jQuery

jQuery Forum

Developing jQuery Core

aseemk

$.getJSON() isn't automatically appending "&callback=?" to my cross-domain URL

Solved

Temporary fix
Not a problem
Analyzing
Need more info
Solved
Working on it

in Developing jQuery Core • 3 years ago

The $.getJSON() documentation states:

If the specified URL is on a remote server, the request is treated as JSONP instead. See the discussion of the jsonp data type in $.ajax() for more details.

The $.ajax() documentation for the jsonp data type states (emphasis mine):

Loads in a JSON block using JSONP. Will add an extra "?callback=?" to the end of your URL to specify the callback.

So it seems that if I call $.getJSON() with a cross-domain URL, the extra "callback=?" parameter should automatically get added. (Other parts of the documentation support this interpretation.)

However, I'm not seeing that behavior. If I don't add the "callback=?" explicitly, jQuery incorrectly makes an XMLHttpRequest (which returns null data since I can't read the response cross-domain). If I do add it explicitly, jQuery correctly makes a <script> request.

Here's an example:

var URL = "http://www.geonames.org/postalCodeLookupJSON" +
"?postalcode=10504&country=US";
function alertResponse(data, status) {
alert("data: " + data + ", status: " + status);
}
$.getJSON(URL, alertResponse);
// alerts "data: null, status: success"
$.getJSON(URL + "&callback=?", alertResponse);
// alerts "data: [object Object], status: undefined"

So what's going on? Am I misunderstanding the documentation or forgetting something?

It goes without saying that this isn't a huge deal, but I'm creating a web API and I purposely set the callback parameter to "callback" in the hopes of tailoring it nicely to jQuery usage.

Thanks!

(This is a duplicate of a Stack Overflow post that hasn't gotten any replies so far, though it did get two votes!)

Replies(8)

dave.meth..

Re: $.getJSON() isn't automatically appending "&callback=?" to my cross-domain URL

3 years ago

What domain is your page on? It's not on a local drive, is it?

aseemk

Re: $.getJSON() isn't automatically appending "&callback=?" to my cross-domain URL

3 years ago

It's not. I'm using JSBin for testing; just include jQuery latest and copy my code above, and you'll get the same results.

dave.meth..

Re: $.getJSON() isn't automatically appending "&callback=?" to my cross-domain URL

3 years ago

I looked for information on jsbin and ajax and couldn't find it. The help page says there's a tutorial but I couldn't find it. Can you set up a standalone page and see if it works there?

aseemk

Re: $.getJSON() isn't automatically appending "&callback=?" to my cross-domain URL

3 years ago

JSBin is really the same -- it evals your code in an <iframe> within the JSBin domain. But just to make sure, I made an explicit file and put it up on the internet, and it's the same behavior.

This is a temporary URL:

http://aseemk.blob.core.windows.net/temp/jquery-jsonp.html

Thanks for looking into this, btw.

Edit: btw, you can look at Firebug to see that one is an XMLHttpRequest and the other is a <script> request. They should both be <script> requests, no? And they should both have "callback=?".

dave.meth..

Re: $.getJSON() isn't automatically appending "&callback=?" to my cross-domain URL

3 years ago

OK, thanks for setting that up. I just wanted to make sure it wasn't due to jsbin and was too lazy to dig further until I knew that. :)

As implemented right now, a request with dataType:"json" is only transformed to jsonp if the url has a "=?" in the url, which your test confirms. A request with dataType:"script" is also transformed to jsonp if the url is remote.

The $.ajax api docs say, "If the fetched data file exists on a remote server, the jsonp type can be used instead. ... When data is retrieved from remote servers (which is only possible using the script or jsonp data types), the operation is performed using a <script> tag rather than an XMLHttpRequest object. " Although it's passive voice, I think the docs are saying that you need to specify jsonp, which you'd need to do rather than using the $.getJSON method. You're not the only one who was confused by this, there's a similar question on the api page for $.getScript.

I can clarify the docs but before doing that I'll move it the the Developing jQuery Core forum to see if this is the intended behavior and/or whether remote dataType:"json" requests should be transformed to jsonp.

aseemk

Re: $.getJSON() isn't automatically appending "&callback=?" to my cross-domain URL

3 years ago

Thanks for your explanation!

Yes, in that case, the docs should be corrected. But also yes, it seems like a *very* sensible, easy, useful and super helpful thing to do if the behavior actually was as documented: if $.ajax() with dataType: "json" could detect cross-domain requests and treat them as "jsonp" automatically, and by extension, if $.getJSON() would automatically treat cross-domain requests as jsonp.

So all in all, consider this a bug report in the current docs but also a feature request. Let me know if I should do anything more on my end or if I can help in any way. Thanks!

aubourg.j..

Re: $.getJSON() isn't automatically appending "&callback=?" to my cross-domain URL

3 years ago

@assemk:

Why should $.ajax (which is called by getJSON under the hoods) append the "&callback=?" for cross-domain json requests?

As of today, and afaik, only Opera doesn't support cross-domain requests: webkit & gecko support it with the new W3C cross-domain XMLHTTPRequest specification and IE through its proprietary XDR object. The former is already supported by jQuery, the latter should be soon (it's in the ajax rewrite). Also, keep in mind you can very well do jsonp request on the same domain. So there is strictly no reason to consider cross-domain json requests and jsonp requests as equivalent since it is, actually, a totally wrong assumption.

Internally, jQuery tests for the presence of "=?" in the url of json requests to control if they happen to be jsonp requests. So whenever a json request has this in its url, it's considered jsonp. Works prefectly fine and as intended.

The documentation is wrong and should be fixed but the behavior is perfectly fine.

dave.meth..

Re: $.getJSON() isn't automatically appending "&callback=?" to my cross-domain URL

3 years ago

Hi, I've updated the docs for jQuery.ajax and jQuery.getJSON to clarify things. If it still needs tweaking you can just post a comment on the page.

Top Reply

Response title

Attachments

jQuery Forum

$.getJSON() isn't automatically appending "&callback=?" to my cross-domain URL

Solved

Replies(8)

Re: $.getJSON() isn't automatically appending "&callback=?" to my cross-domain URL

Re: $.getJSON() isn't automatically appending "&callback=?" to my cross-domain URL

Re: $.getJSON() isn't automatically appending "&callback=?" to my cross-domain URL

Re: $.getJSON() isn't automatically appending "&callback=?" to my cross-domain URL

Re: $.getJSON() isn't automatically appending "&callback=?" to my cross-domain URL

Re: $.getJSON() isn't automatically appending "&callback=?" to my cross-domain URL

Re: $.getJSON() isn't automatically appending "&callback=?" to my cross-domain URL

Re: $.getJSON() isn't automatically appending "&callback=?" to my cross-domain URL

Statistics

Tags

Actions

Related Posts