jQuery and CORS

Question

How should I approach this if the server doesn't respond with JSONP? I've tried several options with $.ajax, but can't get it to work.

CodePen Example

//var url = 'https://coinbase.com/api/v1/currencies/exchange_rates';
var url = 'http://blockchain.info/ticker';
$.ajax({
    type: 'GET',
    url: url,
    //jsonpCallback: 'jsonCallback',
    contentType: 'application/json',
    //async: false,
    //dataType: 'jsonp',

    //xhrFields: { 
    // for CORS?
    //  withCredentials: false
    //},
    success: function (json) {
        debugger;
    },
    error: function (json) {
     debugger;
    }
});

does this help ? http://stackoverflow.com/questions/17318426/cors-cross-domain-ajax-without-jsonp-by-allowing-origin-on-server — Scott Selby, Jan 02 '14 at 15:40
I can't change the server settings, but it does have an example of using XmlHttpRequest that I'm trying out. — AlignedDev, Jan 02 '14 at 16:59

score 5 · Accepted Answer · answered Jan 09 '14 at 02:06

5

It looks like you're trying to send an AJAX request to blockchain.info and retrieve the JSON feed. Luckily they've added support for CORS.

Simply pass the parameter cors=true to the requested url (ex. http://blockchain.info/ticker?cors=true) and you should be able to grab the data.

Looks like CORS are only supported for a few API calls as per https://blockchain.info/api/blockchain_api.

answered Jan 09 '14 at 02:06

Joey Cody

91
3

Does not work for something as simple as https://blockchain.info/address/168FFNnk1GnX25aX4gSukZqRxnemUMu8YW?format=json&cors=true – Smack Jack Oct 21 '16 at 00:39

score 0 · Answer 2 · edited Mar 12 '14 at 03:55

Request:

$.ajax({
            url: "http://yoururl",
            type: "POST",
            crossDomain: true,
            data: JSON.stringify(somejson),
            dataType: "json",
            success: function (response) {
                var resp = JSON.parse(response)
                alert(resp.status);
            },
            error: function (xhr, status) {
                alert("error");
            }
        });

Sample response from server (In Python - Django)

response = HttpResponse(json.dumps('{"status" : "success"}'))
response.__setitem__("Content-type", "application/json")
response.__setitem__("Access-Control-Allow-Origin", "*")

return response

Essentially you have to change the response headers on the server side.

score 0 · Answer 3 · answered Jan 06 '14 at 09:35

It sounds like you're doing a cross-domain request to a server that doesn't support JSONP.

There's a good reason why browsers refuse data from servers that don't want their data to be used in cross-domain requests. If browsers didn't do that, there's be a ton of security problems all over the web. So the server needs to allow this for this to work.

There are basically two ways a server can allow this: the old ugly way through JSONP, but you say it doesn't support that. Though you could still try by changing your url to 'http://blockchain.info/ticker?callback=?' and datatype to jsonp.

But there's also the new, clean way with CORS headers. If the server adds a Accept-Control-Allow-Origin: * header to its response, anyone (using a modern browser) can use the data with a normal Ajax call.

If the server doesn't allow you to use its data, you're out of luck.

jQuery and CORS

3 Answers3

Request:

Sample response from server (In Python - Django)

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