What's the meaning of the comma in a jQuery selector [duplicate]

Answer 1

It sets this as the context from which the query is performed.

An equivalent (and slightly more efficient) way to write it is:

return $(this).find('strong').length == 2;

When I say equivalent, I mean behind the scenes, it is actually flipped around into the version above.

If you remove the 'strong', you won't have a valid selector. You'll be doing:

return $(this).find('').length == 2;

Looks like it just returns an empty jQuery object, which means length will be 0, so you won't get any elements out of the .filter().

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Reference:

http://api.jquery.com/jQuery/

jQuery( selector [, context ] )

context

Type: Element or jQuery

A DOM Element, Document, or jQuery to use as context

Answer 2

If you remove STRONG tag, it would check if any of LI contain string 1 character long, regardless if they encapsulated within STRONG tag. In this case no results would be highlighted. Selectors like $('strong', this) and $(this).find('strong') are pretty much the same.