var A = function() {},
B = function() {},
PR = {};
A.prototype = PR;
B.prototype = PR;
var a = new A(),
b = new B();
var A = function() {},
B = function() {};
A.prototype = new Object();
B.prototype = new Object();
var a = new A(),
b = new B();
blogs.msdn.com/b/ieinternals/archive/2012/05/05/pr...