A step by step example and a jsonp web service to practice on is available at: this post

JSONP is a great away to get around cross-domain scripting errors. You can consume a JSONP service purely with JS without having to implement a AJAX proxy on the server side.

You can use the b1t.co service to see how it works. This is a free JSONP service that alllows you to minify your URLs. Here is the url to use for the service:

http://b1t.co/Site/api/External/MakeUrlWithGet?callback=[resultsCallBack]&url=[escapedUrlToMinify]

For example the call, http://b1t.co/Site/api/External/MakeUrlWithGet?callback=whateverJavascriptName&url=google.com

would return

whateverJavascriptName({"success":true,"url":"http://google.com","shortUrl":"http://b1t.co/54"}); 

And thus when that get's loaded in your js as a src, it will automatically run whateverJavascriptName which you should implement as your callback function:

function minifyResultsCallBack(data) { document.getElementById("results").innerHTML = JSON.stringify(data); } 

To actually make the JSONP call, you can do it about several ways (including using jQuery) but here is a pure JS example:

function minify(urlToMinify) { url = escape(urlToMinify); var s = document.createElement('script'); s.id = 'dynScript'; s.type='text/javascript'; s.src = "http://b1t.co/Site/api/External/MakeUrlWithGet?callback=resultsCallBack&url=" + url; document.getElementsByTagName('head')[0].appendChild(s); } 

A step by step example and a jsonp web service to practice on is available at: this post