jsonp.js

window.jsonpCbs = {};

var jsonp = function(uri, cb) {
	var key = 'cb' + Math.floor( Math.random() * 100000 );

	var cb2 = function() {
		delete window.jsonpCbs[key];
		cb.apply(null, arguments);
	};

	window.jsonpCbs[key] = cb2;

	var scriptEl = document.createElement('script');
	scriptEl.setAttribute('type', 'text/javascript');
	var sep = (uri.indexOf('?') === -1) ? '?' : '&';
	scriptEl.setAttribute('src', [uri, sep, 'jsonp=jsonpCbs.', key].join(''));
	document.head.appendChild(scriptEl);
};