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

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);