troopjs/troopjs-utils — pull request #3 by normanzb (2012-08-29 11:49:27+00:00)
Title: Fix: Array sub class on IE < 8

Fix: On IE < 8, Array.prototype.join() fail to return expected result when the context

A simple test case:
FakeArrayCtor = function(){Array.prototype.push.call(this, 1);}
FakeArrayCtor.prototype = Array.prototype;
fac = new FakeArrayCtor();
fac.join(/)

A article that describe how to sub class Array:
perfectionkills.com/how-ecmascript-5-still-does-not-allow-to-subclass-an-array/