Method overloading

new_gist_file.js

function addMethod(object,name,fn){
  var old = object[name];
  object[name] = function() {
    if(fn.length == arguments.length){
      return fn.apply(this,arguments);
    }
    else if(typeof old == "function"){
      return old.apply(this,arguments);
    }
  };
}