Syncrhonous Cross-Domain AJAX request

Question

Suppose the following directory structure:

/web
    example.html
    example.js
/example.json

I open example.html with my browser and it runs example.js, which tries to load the data in example.json synchronously using the following call:

$.ajax({url: "file:///example.json",
        dataType: "json",
        async: false,
        success: function(data) {
            console.log(data)
        },
        error: function(request, status, error) {
            console.log(request);
            console.log(status);
            console.log(error);
        }
});

This results in an error with message "Access to restricted URI denied" and error code 1012. So far, I have taken a look at Access to restricted URI denied“ code: ”1012 - Cross domain Ajax request and Access to restricted URI denied code: 1012. The first link suggested that I use jQuery's getJSON method, but this method only works asynchronously. The second link suggests some sort of JSONP callback, but I haven't been able to understand how exactly these work.

Note that this problem easily goes away if I move example.json to /web/example.json, but I would like to avoid this due to some circumstances of my actual problem (what I presented here is a simplification of my actual problem).

EDIT: I am trying this JSONP code, but I am still running into the same error:

$.ajax({url: "file:///example.json",
    dataType: "jsonp",
    success: function(data) {
        console.log(data)
    },
    error: function(request, status, error) {
        console.log(request);
        console.log(status);
        console.log(error);
    }
});

Why does it need to be synchronous? Why not just delay execution of specific code until callback function is triggered? — Brad M, Jul 25 '13 at 14:50
The reason for using AJAX is because it is asynchronous. The reason is lost when you make it synchronous :( — Selvakumar Arumugam, Jul 25 '13 at 14:53
@Vega The reason I am using AJAX is because it can load my JSON data, not because it is asynchronous. If there is an alternative that can also load my JSON data, I would be happy to hear about it. — abw333, Jul 25 '13 at 14:55
@Vega There are scenarios where synchronous ajax is the only solution. — Brad M, Jul 25 '13 at 14:57
@abw333 The alternative is your web server requesting the JSON data and serving it to the client. — Brad M, Jul 25 '13 at 14:58
@BradM Making this request synchronous would make my code simpler. I'm actually executing this request inside a for loop and I don't want to do anything until all the requests have fetched their JSON data. Also. I'm not using a web server. This is all local and I would like to keep it that way for simplicity's sake. — abw333, Jul 25 '13 at 14:58
in what scenarios is synchronous the only solution? if synchronous is the only solution, you're working in an environment that needs to be updated/replaced. Back on topic, the cross-domain request you're making will not work in chrome regardless of what you do because it's `file://` unless you started chrome with lesser security settings. I suggest working from two domains rather than a domain and the file system if you want to test a cross-domain request. — Kevin B, Jul 25 '13 at 15:08
Sending ajax requests in a loop while keeping them asynchronous is very easy and maintainable using the promise interface. — Kevin B, Jul 25 '13 at 15:11
@KevinB Lets say a user closes their browser and you want to send an ajax request during the unload event; synchronous is your only option. — Brad M, Jul 25 '13 at 15:12
@KevinB When [compiling synchronous C++ operations to JS](http://stackoverflow.com/questions/16281511/is-there-a-way-to-fake-a-synchronous-xhr-request) (e.g., by using [emscripten](https://github.com/kripken/emscripten/)), sometimes you can only use a synchronous operation. That said, I won't necesarily disagree with your assertion that if you're compiling your C++ into JS that your "environment that needs to be updated/replaced". — apsillers, Jul 25 '13 at 16:08

score 0 · Answer 1 · edited May 23 '17 at 12:06

0

By default cross-domain AJAX requests are not allowed. You need permission from the other server using CORS, or you can use JSONP.

edited May 23 '17 at 12:06

Community

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answered Jul 25 '13 at 14:52

Diodeus - James MacFarlane

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JSONP can't be synchronous though. – Brad M Jul 25 '13 at 14:53
@Diodeus Take a look at the edit I just made to the question. Do you know why it is not working? – abw333 Jul 25 '13 at 15:57

score 0 · Answer 2 · answered Jul 25 '13 at 15:00

0

Your reasoning for using synchronous ajax is misguided. If you want to wait until all ajax requests complete, use the following methodology.

var ajaxRequest1 = $.ajax();
var ajaxRequest2 = $.ajax();
var ajaxRequest3 = $.ajax();
$.when(ajaxRequest1, ajaxRequest2, ajaxRequest3).done(function(){});

This will be far more efficient/faster than executing a series of synchronous ajax requests inside a loop.

answered Jul 25 '13 at 15:00

Brad M

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What if I don't know how many AJAX requests will be executed until runtime? (It depends on user input) – abw333 Jul 25 '13 at 15:12
Then you pass an array/collection of jqXHR objects. `$.when.apply($, ajaxRequestArray)` – Brad M Jul 25 '13 at 15:15
I'll let you know in a few moments :) – abw333 Jul 25 '13 at 15:23
So the change to asynchronous requests worked, but I'm still having the original "Access to restricted URI denied" error. Now I should use JSONP? – abw333 Jul 25 '13 at 15:42
@abw333 Yes, you should use JSONP. – Brad M Jul 25 '13 at 16:14
I'm having difficulties with JSONP. Could you take look at the edit I made to the original question? – abw333 Jul 25 '13 at 16:15
Those web services need to be configured to handle JSONP requests. – Brad M Jul 25 '13 at 16:26
They are not a web service. This is all local. – abw333 Jul 25 '13 at 16:27
Ok, so configure it to handle JSONP. – Brad M Jul 25 '13 at 16:28
let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/34173/discussion-between-abw333-and-brad-m) – abw333 Jul 25 '13 at 16:29

score 0 · Answer 3 · answered Mar 08 '15 at 12:32

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Cross-domain requests and dataType: "jsonp" requests do not support synchronous operation.

Look at documentation here.

answered Mar 08 '15 at 12:32

Ömer Cinbat

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Syncrhonous Cross-Domain AJAX request

3 Answers3