Enum construct

I really miss enumerable flags/bit masks from C#. Something like:

var enum = new Enum('a', 'b', 'c', 'd');
var mask = enum.a | enum.b;

if (mask & enum.a) // true
if (mask & enum.c) // false
if (mask & enum.b) // true

See https://developer.mozilla.org/en/JavaScript/Reference/Operators/Bitwise_Operators#section_13 for some examples.
