Override function (e.g. “alert”) and call the original function?

Question

I would like to override a Javascript built-in function with a new version that calls the original (similarly to overriding a method on a class with a version that calls

Answer 1

I'm assuming your question is how do you overwrite a built-in and still be able to call it. First off as a disclaimer, you should never overwrite built ins unless you have a good reason for doing it since it will make it impossible to debug/test.

This is how you would do it:

window._alert = window.alert;
window.alert = function(str) { 
     if(console) console.log(str);
     window._alert(str);
}