How to detect a JavaScript function with a certain signature has been registered?

Question

Say you have two functions with the following signatures:

1. addClass( class )
2. addClass( class, duration )

Answer 1

There is no native method overloading in JavaScript. You can create your own, though: http://ejohn.org/blog/javascript-method-overloading/

(Update 11/5/15: The link seems to be dead, here's the Google Cache version)

So if you do

function addClass( class ) { console.log('1 arg'); };
function addClass( class, duration ) { console.log('2 args'); };

the second one overwrites the first one. So even if you call "addClass(1)", the output will still be "2 args". Same as doing

someObject.addClass = function(a) {...}
someObject.addClass = function(a, b) {...}

The first "version" will be lost.