Question

How can I manipulate the prototype of a predefined object (for example an Array) so that it does something when creating instances of that object?

Simply I want to alert('an array was created!') whenever an Array is instantiated.

Answer 1

You can try to override Array with your own function. It seems to work when doing new Array, but not when doing [].

(function() {
    var _ac = Array;
    Array = function() {
        alert('an array was newed!');
        return _ac.apply(this, arguments);
    };
}());

DEMO: http://jsfiddle.net/DAg9A/