jsonp.js

var myUtil = (function() {
    var jsonpMethods = {},
        head = document.getElementsByTagName('head')[0],
        jsonpCount = 0;
 
    var getJSON = function(url, params, callbackFuncName, callback) {
        var paramsArr = [],
            jsonp = 'jsonp_' + new Date().getTime() + '_' + (jsonpCount++);
        for (var key in params) {
            paramsArr.push(encodeURIComponent(key) + '=' + encodeURIComponent(params[key]));
        }
        url += ((url.indexOf('?') !== -1) ? '&' : '?') + callbackFuncName + "=myUtil.jsonpMethods." + jsonp + "&" + paramsArr.join("&");
        jsonpMethods[jsonp] = function(data) {
            delete jsonpMethods[jsonp];
            head.removeChild(script);
            callback(data);
        };
        var script = document.createElement('script');
        script.charset = "UTF-8";
        script.src = url;
        head.appendChild(script);
        return true;
    };
 
    return {
        jsonpMethods: jsonpMethods,
        getJSON: getJSON
    };
})();
 
myUtil.getJSON("xxx.php", {}, "jsoncallback", function(data){
    console.log(data);
});