How to make a JSONP request from Javascript without JQuery?

function foo(data)
{
    // do stuff with JSON
}

var script = document.createElement('script');
script.src = '//example.com/path/to/jsonp?callback=foo'

document.getElementsByTagName('head')[0].appendChild(script);
// or document.head.appendChild(script) in modern browsers

I have a pure javascript library to do that https://github.com/robertodecurnex/J50Npi/blob/master/J50Npi.js

Take a look at it and let me know if you need any help using or understanding the code.

Btw, you have simple usage example here: http://robertodecurnex.github.com/J50Npi/