var $ = {     getJSON: function(url, params, callbackFuncName, callback){         var paramsUrl ="",             jsonp = this.getQueryString(url)[callbackFuncName];         for(var key in params){             paramsUrl+="&"+key+"="+encodeURIComponent(params[key]);         }         url+=paramsUrl;         window[jsonp] = function(data) {             window[jsonp] = undefined;             try {                 delete window[jsonp];             } catch(e) {}             if (head) {                 head.removeChild(script);             }             callback(data);         };         var head = document.getElementsByTagName('head')[0];         var script = document.createElement('script');         script.charset = "UTF-8";         script.src = url;         head.appendChild(script);         return true;     },     getQueryString: function(url) {         var result = {}, queryString = (url && url.indexOf("?")!=-1 && url.split("?")[1]) || location.search.substring(1),             re = /([^&=]+)=([^&]*)/g, m;         while (m = re.exec(queryString)) {             result[decodeURIComponent(m[1])] = decodeURIComponent(m[2]);         }         return result;     } };

var url = "http://xxx.xxx.xxx?callback=jsonp123"; var params = {     a:1,     b:2 }; $.getJSON(url, params, "callback", function(data){     //todo });