TypeError：xy不是函数，显然它是

Question

I'm experiencing a strange behavior off of javascript yet again. I find this to be extremely illogical and confusing.

I probably did kind of a mess drawing over the picture but briefly, you see that $$('h2') is clearly an object which has a method on , or in javascript language a property on which turns out to be a function, however when I try to access that function I get a TypeError?

MY QUESTION IS: Why am I getting this error when obviously the object does have a property called on which is a function?

EDIT: Here's the on function

on: function(event, func) {
        this.node.addEventListener(event, func, false);
    }

Answer 1

You've missed the leading [ in your console output. The object you're printing is an array whose first element has an on property.

You likely want $$('h2')[0].on(...) instead.