John Siu Blog

Some regex I used.

IPv4

Match IPv4 in digit:

\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}

Match IPv4 in alphanumeric:

\w{1,3}\.\w{1,3}\.\w{1,3}\.\w{1,3}

URL

With http/https

https?://[^\[\]()\s]*

Optional http/https

(https?:)?//[^\[\]()\s]*

Internal link

/[^/][^\[\]()\s]*

Markdown link not close with /

Match ](/…), while ... don’e contain )# and link not closed with /.

](/blog/test) : Not match

](/blog/test/) : Match

\]\(/[^/][^)#]*[^/]\)

Replace 1 but not 2 consecutive characters

General form:

(?<!x)x(?!x)

Match 1 newline but not 2 in a row:

(?<!\n)\n(?!\n)

Match 1 newline but not 2 in a row and also not following a . or ":

(?<!(\n|”|"|\.))\n(?!\n)