Prototyping Object in Javascript breaks jQuery?

Question

I have added a simple .js file to my page that has some pretty mundane common-task sort of functions added to the Object and Array prototypes.

Through trial and error, I've figured out that adding any function to Object.prototype, no matter it's name or what it does causes Javascript errors in jQuery:

The culprit?

Object.prototype.foo = function() {
    /*do nothing and break jQuery*/
};

The error I'm getting line 1056 of jquery-1.3.2.js, in the attr:function { } declaration:

/*Object doesn't support this property or method*/
name = name.replace(/-([a-z])/ig, function(all, letter) {
            return letter.toUpperCase();
        });

Apparently G.replace is undefined.

While it's obvious that there's something I'm just not wrapping my head around with prototyping, I'm failing miserably to figure out what it is.

To be clear, I'm not looking for a workaround, I have that handled... what I'm looking for is an answer to Why?. Why does adding a function to Object.prototype break this bit of code?

Answer 1

If it's simply a case of messing up for...in loops, can't you use Object.defineProperty to add your fn without making it enumerable?

So:

Object.defineProperty(Object.prototype, "foo", { 
    value: function() {
        // do stuff
    },
    enumerable : false
});

Seems to work for me. Would this still be considered bad form?