javascript: what is the "default" method?

I was browsing through the NPAPI documentation and I stumble on InvokeDefault method. Of course I googled a bit but without turning re开发者_如何转开发lated results.

So the questions are to the Javascript experts:

1) What is a "default" method on a JS object?

2) How can one declare & define such method?

I'm not sure, but I think this is the default browser behaviour, for example, when you click a check box, it toggle that box, if you click a textfield, it put the cursor in it and so on.

I don't think you can do anything with it except invoking it if you intercept the event.