Is this valid JSON markup?

Question

Hello. I am attempting to get some information from a russian shipping website. Being a n00b to JSON/Jquery/Internets I am stuck getting the data into json format.

Following the company's API, I go to the URL: http://emspost.ru/api/rest/?callback=json&method=ems.calculate&from=city--abakan&to=city--anadyr&weight=1

This returns:

json({"rsp":{"stat":"ok","price":"750","term":{"min":5,"max":9}}})

Following Jquery's docs, I have tried:

<script>$.getJSON("http://emspost.ru/api/rest/?callback=json&amp;method=ems.calculate&amp;from=city--abakan&amp;to=city--anadyr&amp;weight=1",
        function(data){
        alert(data);
        });</script>

This returns null. Any idea what I'm doing wrong?

Answer 1

You are using a callback function (callback=json) which runs the function json when it loads.

Try GETting this instead:

http://emspost.ru/api/rest/?method=ems.calculate&from=city--abakan&to=city--anadyr&weight=1

Btw, is your request crossdomain? If so, an xhr is not suggested.

Answer 2

Use callback=? instead, like this:

$.getJSON("http://emspost.ru/api/rest/?callback=?&method=ems.calculate&from=city--abakan&to=city--anadyr&weight=1",
function(data){
  alert(data);
});

Then you'll get your object in the alert :) JSONP works by taking that callback in the querystring and calling that function (which doesn't exist, unless you made a function json() {} when it returns. When you do ?callback=? jquery dynamically names that success function you gave to $.getJSON() and replaces it, like this: ?callback=FunctioNameGiven, so it'll actually run correctly.

If you think about how it runs, it's basically:

<script type="text/javascript">
  //returned javascript here, e.g. FunctioNameGiven({ object data });
</script>

This is done so it's a GET request, and not limited by same-origin policy rules, that's how JSONP works where a normal JSON request gets blocked :)