在JavaScript中从外部来源获取json

Question

Json issues with javascript and jquery. Trying to load some JSON using javascript.

I have it working using:

See it here: http://jsfiddle.net/5pjha/789/

var url = "http://maps.googleapis.com/maps/api/geocode/json?address=1600+Amphitheatre+Parkway,+Mountain+View,+CA&sensor=true";

$.getJSON(url, function (json) {
    alert(JSON.stringify(json.results));
});

But it dosnt work on the following urls, why is this?

https://poloniex.com/public?command=return24hVolume

https://bittrex.com/api/v1/public/getmarkets

https://api.mintpal.com/v1/market/summary/

Are the following urls not correct JSON ?

Thanks

Answer 1

The google's api set the Access-Control-Allow-Origin header to * , so you could access it by cross domain.

While other urls you provided do not, so you will got an error like below:

XMLHttpRequest cannot load https://api.mintpal.com/v1/market/summary/ . No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin ' http://fiddle.jshell.net ' is therefore not allowed access.

Answer 2

I believe the issue is down to whether or not the servers you are requesting your JSON from have cross-origin resource sharing ( CORS ) enabled.

you can see in the headers from the google service that they set Access-Control-Allow-Origin:* This is not the case for teh other URL's you list.

To get around this you will need some form of proxy so that you can request from a server either on the same domain or a server that enables CORS.

Answer 3

For ajax request to any server, You need to define Access-Control-Allow-Origin header for client. which is absent in given. You need to define origin of XMLHttp request in server who can request.

For more info refer this link