Is there any possibility to change the __proto__ property of an object in IE9 or IE10? Or is MS still not planning to include it in their JS engine?
__proto__
I n
I'm not sure what exactly it is you're after since your question didn't specify, but for most uses of proto, you should be able to use prototype.
prototype
var foo = new Bar(); //this also affects foo Bar.prototype.baz = something;