What does this regex (\/?) mean?

Question

The following code is taken from Jon Resig's book Secrets of JavaScript Ninja

var html = "<div class='test'><b>Hello</b> <i>world!</i></div>";
var results = html.match(/<(\/?)(\w+)([^>]*?)>/);

I want to understand the meaning of the first capture (within the parenthesis) ie (\/?).

Answer 1

It matches an optional slash. The slash needs to be escaped because slashes also serve as delimiters in JavaScript regex literals.

It's not really useful to surround it with capturing parentheses. \/? would work as well (unless you later on want to check whether you have matched an opening or a closing tag).

Answer 2

It is either exactly one / or nothing. / has to be escaped inside regexp because it means "end of regexp" when unescaped.