jsonp implementation

Implementation code:

( function (global) {
     var id = 0 ,
        container = document.getElementsByTagName("head")[0];

    function jsonp(options) {
        if(!options || !options.url) return;

        var scriptNode = document.createElement("script"),
            data = options.data || {},
            url = options.url,
            callback = options.callback,
            fnName = "jsonp" + id++;

        // Add callback function 
        data["callback"] = fnName;

        // 拼接url
        var params = [];
        for (var key in data) {
            params.push(encodeURIComponent(key) + "=" + encodeURIComponent(data[key]));
        }
        url = url.indexOf("?") > 0 ? (url + "&") : (url + "?");
        url += params.join("&");
        scriptNode.src = url;

        // Passed is an anonymous callback function, if it is to be executed, it is exposed as a global method 
        global[fnName] = function (ret) {
            callback && callback(ret);
            container.removeChild(scriptNode);
            delete global[fnName];
        }

        // Error handling 
        scriptNode.onerror = function () {
            callback && callback({error:"error"});
            container.removeChild(scriptNode);
            global[fnName] && delete global[fnName];
        }

        scriptNode.type = "text/javascript";
        container.appendChild(scriptNode)
    }

    global.jsonp = jsonp;

})(this);

use:

jsonp ({
    url : "www.example.com",
    data : {id : 1},
    callback : function (ret) {
        console.log (ret);
    }
});