Extending Object causes jQuery error
===

So I wrote a function to extend Objects to count how many entries are within them, so it may be used as such:

    test = {"foo": "bar", "baz": 7, "darth": "maul"}
    
    test.count()
    => 3

I wrote the code as such:

    Object.prototype.count = function() {
      var count = 0, key;
      for (key in this) {
        if (this.hasOwnProperty(key)) {
          count++;
        }
      }
      return count;
    }

This is my first attempt at extending with prototype, and I'm getting this error from within jQuery.js:

    Uncaught TypeError: Object function () {
      var count = 0, key;
      for (key in this) {
        if (this.hasOwnProperty(key)) {
          count++;
        }
      }
      return count; 
    } has no method 'replace'

The stacktrace points back to where I call `css` on a jQuery object onLoad:

    $img.css({left: 20, top: 50});

Not that I think there's anything specific about that line, but I thought it may be good to provide.

Is there something I'm doing wrong here?