I've been debugging a site to find the source of long page loading times, and I've narrowed it down to a regex that's used to extract URLs from text:
/(?:([\w+.-]+):\/\/|(?:www\.))[^\s<]+/g
This takes about 3 seconds to run on a large block of text. I found out that if I add the inverse of the first clause to the start of the regex ((?:[^\w+.-]|^)), it runs almost instantly:
/(?:[^\w+.-]|^)(?:([\w+.-]++):\/\/|(?:www\.))[^\s<]+/gx
It seems to me like the added clause shouldn't affect …