sandbox.js

function del(obj)
{
var
	properties = Object.getOwnPropertyNames(obj),
	l = properties.length
;
	while (l--)
	{
		try {
			delete obj[properties[l]];
		} catch(e) {}
	}
}
	
/* jshint evil:true */

var iframe = document.createElement('IFRAME');
iframe.style.display = 'none';
iframe.src = "about:blank";
document.body.appendChild(iframe);

var w = iframe.contentWindow;
var evil = w.eval;
function sandbox(a) {
	return evil.call(w, 
		'(function(window, document, location) { "use strict"; ' +				 
		'return (' + a + '); }).call(undefined);'
	);
};

del(w);