异步加载外部Javascript

$.extend({
        loadScript : function (url, data, callback) {
            if ($.isFunction(data)) {
                callback = data;
                data = null;
            }
            if (data != null) {
                var urlInfo = url.match(/^([^?#]+)\?*([^#]*)#?(.*)$/);
                url = urlInfo[1];
                var query = $.trim(urlInfo[2]);
                var fragment = $.trim(urlInfo[3]);
                if (typeof data === 'object') {
                    data = $.param(data);
                }
                if (typeof data === 'string') {
                    query += (query == '' ? data : ("&" + data));
                }
                query === '' || (url += ('?' + query));
                fragment === '' || (url += ('#' + fragment));
            }
            
            var script = document.createElement("script");
            script.type = "text/javascript";
            script.src = url;
            script.onload = script.onreadystatechange = function () {
                if (!document.all || document.all && this.readyState == "loaded") {
                    if ($.isFunction(callback)) {
                        callback();
                    }
                }
            }
            document.getElementsByTagName("head")[0].appendChild(script);
            delete script;
        }
    });