Assuming I deleted window.alert, how would I get it back?

Question

Assume I do this in javascript

delete window.alert;
// returns true

then the output of console.log(window.alert); will be \"

Answer 1

How do you 'undelete' window.alert?

You would have needed to save a reference of the function:

var windowAlertBackup = window.alert;

And then:

window.alert = windowAlertBackup;

What is actually happening?

Any native window function is actually implemented by the javascript interpreter. In javascript window.alert is a pointer to that native function. window.alert is the only default reference to the native window.alert code.