Surely, it is impossible to create something purely innovative in js (most of the time).

Take, for example a DHTML tooltip, or a draggable layer. Most probably it has been implemented by hundreds of different developers
in hundreds of different ways.

imho, inspiration is not copying the code and altering it to suit your needs.

Here is what I think the proper way of doing it should be:

i. observe the page what it does etc.
look at the source code if necessary.

ii. then close everything and implement the idea in your way (i.e. as they say in literature classes ‘express it in your own words’ )

iii. And cite the owner somewhere (in the source code, on your site etc) if you think the idea is original and unique.

You are not Siamese Twins with that guy, are you :)