Get unique keys in nested object

keys.js

function getKeys(obj) {
	var keys = Object.keys(obj);
	keys.forEach(function(val) {
		if (obj[val] instanceof Object) {
			keys = keys.concat(getKeys(obj[val]));
		}
	});
	return keys;
}

function getUniqueKeys(obj) {
	var keys = getKeys(obj);
	keys = keys.filter(function (e, i, keys) {
	    return keys.lastIndexOf(e) === i;
	});
	return keys;
}

alert(getUniqueKeys({
	key1: 'one',
	key2: {
		key1: {
			another: 42
		}
	}
})); //produces "key2,key1,another"