The JSONP Utility is a specialized API for communicating with web
            services that provide JSON responses wrapped in a callback
            function.  A typical JSONP request URL might look like
            "http://example.com/service.php?callback=handleData" and
            receive a text response in the form of
            handleData({"records":[....]});.
        
            The nature of YUI 3's sandbox model complicates JSONP transactions
            because JSONP relies on a global access point to process the
            response, but YUI 3 implementation code is typically wrapped in a
            use(...) callback and is therefore not globally
            accessible.  The JSONP module provides a proxy system for
            channeling JSONP responses back into your YUI instance sandbox.
        
Security Note: JSONP is an inherently unsecure communication method, since it involves the transfer of unvalidated JavaScript. It is by convention alone that the format is associated with JSON, but in reality, the response can include any arbitrary JavaScript, potentially opening your page to attack. Be cautious about which services you communicate with via JSONP. For safe JSON communication, use the JSON module in conjunction with the IO module wherever possible.
Getting Started
To include the source files for JSONP and its dependencies, first load the YUI seed file if you haven't already loaded it.
<script src="http://yui.yahooapis.com/3.5.1/build/yui/yui-min.js"></script>
Next, create a new YUI instance for your application and populate it with the
modules you need by specifying them as arguments to the YUI().use() method.
YUI will automatically load any dependencies required by the modules you
specify.
<script>
// Create a new YUI instance and populate it with the required modules.
YUI().use('jsonp', 'jsonp-url', function (Y) {
    // JSONP is available and ready for use. Add implementation
    // code here.
});
</script>
For more information on creating YUI instances and on the
use() method, see the
documentation for the YUI Global Object.
Using the JSONP Utility
Instantiation and the Y.jsonp method
    The JSONP utility provides the Y.jsonp(url, callback) method
    for single transactions as well as a Y.JSONPRequest class to
    manage reusable connections.
    The first argument to either the Y.jsonp method or the
    Y.JSONPRequest constructor is the URL of the JSONP service,
    and the second is a callback function or configuration
    object that contains a callback function.  When the service responds
    with the data, the callback will be executed with the response data as the
    first parameter.
In place of the JSONP callback name in the URL, include the string "{callback}". This placeholder will be used for a proxy function that will route the data to your callback.
// instead of service.php?callback=handleJSONP
var url = "http://example.com/service.php?callback={callback}";
function handleJSONP(response) {
    // response is a JavaScript object. No parsing necessary
    Y.one("#output").setContent(response.outputHTML);
}
Y.jsonp(url, handleJSONP);
// or
var service = new Y.JSONPRequest(url, handleJSONP);
service.send();
Sending JSONP requests
    Y.jsonp(url, callback) will dispatch the request immediately.
    JSONPRequest instances will dispatch the request each time their
    send() method is called.
// request sent immediately Y.jsonp(url, handleJSONP); // No request sent var service = new Y.JSONPRequest(url, handleJSONP); // ...until now service.send(); // ...and now again service.send();
    Y.jsonp(url, callback) is a convenience wrapper to instantiate
    a JSONPRequest instance and call its send() method.
    This will generate a request to a URL like this one (note that the
    {callback} placeholder has been replaced with a dynamically
    generated callback name):
http://example.com/service.php?callback=YUI.Env.JSONP.yui_3_3_0_1_1294184187597423
The server will then be expected to respond with a JavaScript value wrapped in a call to that function, like this:
YUI.Env.JSONP.yui_3_3_0_1_1294184187597423({"foo":"bar"});
Configuring the connection
    The second argument to either Y.jsonp or the
    Y.JSONPRequest constructor can be a success callback function
    or for more control, it can be a configuration object.  The supported keys
    of this object are:
| Property | Description | 
|---|---|
| timeout | This value, defined as milliseconds, is a time threshold for
                the transaction (e.g., { timeout: 2000 }). When
                this limit is reached, the transaction'son.timeoutcallback will be executed if
                supplied. | 
| context | Defines what will be " this" in the
                callbacks.  If undefined, the default will be the JSONPRequest
                instance. | 
| args | An array of additional arguments that will be passed to the callbacks as second, third, and so on arguments. | 
| on | 
                    Required. This object defines the
                    callbacks to be used for the transaction.  At least an
                     
 | 
| format | Preprocessor function to stitch together the supplied URL
                (first argument), the proxy function name (internally
                generated), and any additional arguments passed to send().  See Customizing the
                JSONP URL for more detail. | 
This is an example of a configuration object, with a set of properties defined.
var url     = "http://example.com/service.php?callback={callback}",
    service = new Y.JSONPRequest(url, {
        on: {
            success: MyApp.handleJSONP,
            timeout: MyApp.handleTimeout
        },
        context: MyApp
        timeout: 3000,          // 3 second timeout
        args: [new Date(), 100] // e.g. handleJSONP(data, date, number)
    });
service.send();
// or
Y.jsonp(url, {
    on: {
        success: MyApp.handleJSONP,
        timeout: MyApp.handleTimeout
    },
    context: MyApp
    timeout: 3000,          // 3 second timeout
    args: [new Date(), 100] // e.g. handleJSONP(data, date, number)
});
Parsing the callback from the URL
    An extension for the jsonp module is the
    jsonp-url module which provides a few additional features.
- 
        If you have a global function or a function available from the YUI
        instance (e.g. Y.MyApp.handleJSONP), you can include the name in the URL and omit the second parameter entirely.
- The URL passed as the first parameter need not include the "{callback}" string. If it is not found, it will look for "callback=", then fall back to adding the query parameter onto the URL.
Y.MyApp.handleJSONP = function (data) {
    Y.one("#output").setContent(data.outputHTML);
};
Y.jsonp("http://example.com/service.php?callback=Y.MyApp.handleJSONP");
// or
Y.jsonp("http://example.com/service.php", {
    context: Y.MyApp,
    on: {
        success: Y.MyApp.handleJSONP,
        failure: Y.MyApp.handleFailure
    }
});
Customizing the JSONP URL
    The default URL formatter simply replaces the "{callback}"
    placehold with the name of the generated proxy function.  If you want to
    customize the URL generation process, you can provide a format
    function in the configuration.  The function will receive the configured
    URL (with "{callback}" placeholder), the string name of the proxy
    function, and any additional arguments that were passed to
    send().
// Our custom formatter will expect a URL with an additional placeholder for
// username that must be supplied in send("bill");
// e.g. http://example.com/bill/json?fn=YUI.Env.JSONP._12345
function prepareJSONPUrl(url, proxy, username) {
    return Y.Lang.sub(url, {
        callback: proxy,
        name: username || "user"
    });
}
var url = "http://example.com/{name}/json?fn={callback}";
var service = new Y.JSONPRequest(url, {
        format: prepareJSONPUrl,
        on: {
            success: handleJSONP
        }
    });
service.send("apipkin");
service.send("tivac");
service.send("razass");
Known Issues
- Unlike the XMLHttpRequest calls generated by the IO utility, JSONP requests can't be aborted, since they rely on dynamic script insertion (which provides less low-level control than XHR). Keep this in mind when deciding which method to use.
- Since most browsers don't enforce execution order for dynamically inserted scripts, JSONP callbacks may not be called in the same order that the requests were sent. On the other hand, some browsers do enforce execution order, so in these browsers a slow request may block the execution of subsequent JSONP callbacks.