Looks like Safari doesn't support lookbehind yet (that is, your (?<=\/)). One alternative would be to put the / that comes before in a non-captured group, and then extract only the first group (the content after the / and before the #).
/(?:\/)([^#]+)(?=#*)/
Also, (?=#*) is odd - you probably want to lookahead for something (such as # or the end of the string), rather than a * quantifier (zero or more occurrences of #). It might be better to use something like
/(?:\/)([^#]+)(?=#|$)/
or just omit the lookahead entirely (because the ([^#]+) is greedy), depending on your circumstances.
