Call native javascript function that has been "erased" by the web page

Question

Let's say a web page did this:

window.alert = console.info;

How can I, through browser console, recover the original alert method to get the modal back?

I tried accessing the window.prototype but it does not exist. I would also like to know if such process exist in general (like, if String.* was erased/redefined by a website or if website made a console.log = window.alert).

Answer 1

What you can do, is create an iframe attach it to page and then copy alert method from that iframe

//someone did this
window.alert = null;

//you are doing this
var frame = document.createElement('iframe');
document.body.appendChild(frame);
window.alert = frame.contentWindow.alert.bind(window);
document.body.removeChild(frame);