simple JSONP support

JSONP.js

/**
 * simple JSONP support
 *
 *     JSONP.get('https://api.github.com/gists/1431613', function (data) { console.log(data); });
 *     JSONP.get('https://api.github.com/gists/1431613', {}, function (data) { console.log(data); });
 *
 * gist: https://gist.github.com/gists/1431613
 */
var JSONP = (function (document) {
    var requests = 0,
        callbacks = {};

    return {
        /**
         * makes a JSONP request
         *
         * @param {String} src
         * @param {Object} data
         * @param {Function} callback
         */
        get: function (src, data, callback) {
            // check if data was passed
            if (!arguments[2]) {
                callback = arguments[1];
                data = {};
            }

            // determine if there already are params
            src += (src.indexOf('?')+1 ? '&' : '?');

            var head = document.getElementsByTagName('head')[0],
                script = document.createElement('script'),
                params = [],
                requestId = requests,
                param;
            
            // increment the requests
            requests++;

            // create external callback name
            data.callback = 'JSONP.callbacks.request_' + requestId;
            
            // set callback function
            callbacks['request_' + requestId] = function (data) {
                // clean up
                head.removeChild(script);
                delete callbacks['request_' + requestId];

                // fire callback
                callback(data); 
            };
            
            // traverse data
            for (param in data) {
                params.push(param + '=' + encodeURIComponent(data[param]));
            }

            // generate params
            src += params.join('&');

            // set script attributes
            script.type = 'text/javascript';
            script.src = src;

            // add to the DOM
            head.appendChild(script); 
        },

        /**
         * keeps a public reference of the callbacks object
         */
        callbacks: callbacks
    };
})(document);