jQuery difference between :eq() and :nth-child()

Question

In jQuery, what are some of the key differences between using :eq() and :nth-child() to select any elements ?

Also in general, for the starting index, in which case

Answer 1

:eq is array indexed based, so it starts from 0. It is also not part of the Css specification.

Whereas :nth-child is part of the Css specification and refers to the element position in a DOM tree.

In terms of usage, they both do the same thing.

Demo here