Show all global variables, excluding native browser ones

script.js

(function() {
	var windowKeys = Object.keys(window),
		iframe = document.createElement('iframe'),
		cleanWindowKeys,
		customVars;

	document.body.appendChild(iframe);
	cleanWindowKeys = Object.keys(iframe.contentWindow);
	customVars = windowKeys.filter(function(key) {
		return (cleanWindowKeys.indexOf(key) === -1);
	});

	return customVars;
}());