what is $.expr[":"] in javascript or jQuery?

Question

here is the link to original code: http://css-tricks.com/snippets/jquery/make-jquery-contains-case-insensitive/#comment-518214

http://css-tricks.com/snippets/jquery/make-jquery-contains-case-insensitive/#comment-518214

1) in th above code, what is $.expr[:]? 2) what is $.expr.createPseudo?

I can't find any document about it!!! Why they provide this without document? very frustrated!!!!!!!!!!!

Answer 1

1) in th above code, what is $.expr[:]? 2) what is $.expr.createPseudo?

It's how you extend Sizzle selectors. See the docs.

Sizzle is the DOM query engine used by jQuery.