Override function (e.g. "alert") and call the original function?
javascript, overriding
Solution
Store a reference to the original function in a variable:
(function() {
var _alert = window.alert; // <-- Reference
window.alert = function(str) {
// do something additional
if(console) console.log(str);
//return _alert.apply(this, arguments); // <-- The universal method
_alert(str); // Suits for this case
};
})();
The universal way is `<original_func_reference>.apply(this, arguments)` - To preserve context and pass all arguments. Usually, the return value of the original method should also be returned.
However, it's known that `alert` is a void function, takes only one argument, and does not use the `this` object. So, `_alert(str)` is sufficient in this case.
Note: IE <= 8 throws an error if you try to overwrite `alert`, so make sure that you're using `window.alert = ...` instead of `alert = ...`.
Problem
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 `super` in many languages). How can I do this? For example... ``` window.alert = function(str) { //do something additional if(console) console.log(str); //super.alert(str) // How do I do this bit? } ```