Javascript regular expression for extracting Youtube video ids

Question

The following code is used to get Youtube video ids in order to get a thumbnail image.

What is the reasoning behind the first regular expression and what is it doing

Answer 1

If you are referring to...

results = url.match("[\\?&]v=([^&#]*)");

Then it is matching a literal \, ? or & followed by literal v= followed by a capturing group which is capturing 0 or more of any characters that are not & or #.