a simple and pure javascript jsonp function

jsonp.js

function loadJsonp(url, callback) {
    var callbackName = 'jsonp_callback_' + Math.round(100000 * Math.random());
    window[callbackName] = function (data) {
        delete window[callbackName];
        document.body.removeChild(script);
        callback(data);
    };

    var script = document.createElement('script');
    script.src = url + (url.indexOf('?') >= 0 ? '&' : '?') + 'callback=' + callbackName;
    document.body.appendChild(script);
}