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Comment by crescentfresh | Hacker News Reader

The payload is not JSONP and strikes me as a bit impractical:

    Geo = { /* object literal */ }

I assume this service is meant to be consumed via <script> tag injection. Without a JSONP-style callback parameter, what are consumers to do, inject-then-poll until a "Geo" object is found in the global scope?

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    <script src="http://geoiplookup.wikimedia.org/"></script>
    <script>geoloaded()</script>
    </body></html>

D'oh!

The approach of dynamically generating a callback script is more robust than pure JSONP. If your URL returns an error (e.g., 404), you immediately notice, instead of waiting for the time-out. These days, my usual approach looks something like this in flight:

    <script type="text/javascript">
        var response = undefined;
    </script>
    <script type="text/javascript" src="...">
       // response = { .... };
    </script>
    <script type="text/javascript">
       _callbacks[1234](response); // response == undefined means error
       response = undefined;       // allow garbage collection
    </script>

It's a bit more administration, but I really like not having to worry about dynamic callback names, delayed errors, or non-existent callback functions any more.

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