perf: use isIPv6 for checking if hostname is isIPv6

[Uzlopak]

trivial change. isIP will first run isIPv4 and then isIPv6. Also both are basically calling regexes on node. So by calling isIPv6 directly we improve the performance.

[ronag]

But this will fail on ipv4 addresses now?

[Uzlopak]

Nope. It can not be a IP v4. This is basically "unpacking" a IPv6 from the bracket notation. Like http://[::1]:3000. hostname is then [::1] but needs to be ::1. So this is detecting the wrapping with brackets by checking the if it is starting with a bracket etc..

An IPv4 would not be valid.

See RFC 3986, section 3.2.2.

   A host identified by an Internet Protocol literal address, version 6
   [RFC3513] or later, is distinguished by enclosing the IP literal
   within square brackets ("[" and "]").  This is the only place where
   square bracket characters are allowed in the URI syntax.  In
   anticipation of future, as-yet-undefined IP literal address formats,
   an implementation may use an optional version flag to indicate such a
   format explicitly rather than rely on heuristic determination.