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Cross Domain Ajax/jQuery Scripting with YQL

Apparently I am late to the party on this topic, but it is tremendously cool, so it warrants a blog post.

The pain:

You want to call a remote website/service/etc. using ajax / jquery, but it kinda just never does anything.

The reason:

Cross site scripting is a no-no!  If the site you are talking to is in a different domain, most (good) browsers will block the request, and often will do so silently so you have no clue what is going on.


The solution:

Yahoo's wonderful YQL (Yahoo Query Language) lets you do some cool stuff. You can essentially "query" the content of a URL, like so:  

select * from html where url="http://www.cnn.com"

and you can do it all from javascript!  This is cool stuff, because now your ajax enabled web apps and mobile apps can utilize public web services, apis, and such to enhance your app's functionality, all without building server-side code.

So to do this, all you need is a nifty javascript function like so:

function requestRemoteHtml( url, callback ) {
   
    yql = 'http://query.yahooapis.com/v1/public/yql?q=' + encodeURIComponent('select * from html where url="' + url + '"') + '&format=xml&callback=?';

    $.getJSON(yql, function(data) {
        if ( data.results[0] ) {
            data = data.results[0].replace(/<script[^>]*>[\s\S]*?<\/script>/g,'');
           
            if ( typeof callback === 'function' ) {
                callback(data);
            }
        }
       
        else throw new Error('Nothing returned from getJSON.');
    });   
}


You will need jQuery to get the $.getJSON function, but the YQL stuff is wide open, so if you really wanted to use it without jQuery, you certainly could.  

Pass in the URL you want to query (it can contain GET variables as well), and specify a javascript function as a callback and let it fly.

As always, use this knowledge for good, not evil.

References:




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