[jQuery] using functions as extensions - why does FF not take it?

[jquertil]

has anyone had the following problem before?

VERSION 1 =================// works in IE and FF
myFunction(){
...
}
document.onmousedown=myFunction;



VERSION 2 =================// works in IE but not in FF
jQuery.fn.extend({
  myFunction: function() {
  ...
  }
});
$(document).mousedown(function(){
  $().myFunction();
});