linkify @mentions and #hashtags in a tweet

annotated.js

function(
  a // the text of the tweet to be enlinked
){
  return a.replace( // replace
    /\b[@#]\w+/g,     // any mention/hashtag
    function(
      b,            // the matched mention/hashtag
      c             // placeholder
    ){
      c = "twitter.com/";   // the core twitter url
      return b.link(        // put the match in a link to
        "//" + (            // the "//" protocol, +
          b[a = "search"]   // match the url, reusing for "search"
          ("#")             // if the match starts with "#"
            ? c             // twitter.com/, or otherwise
            : a + "." + c + // search.twitter.com/ +
              a + "?q="     // search?q=
        ) +                 // and then finally, +
        b                   // the mention/hashtag.
      )
    }
  )
}

index.js

function(a){return a.replace(/\b[@#]\w+/g,function(b,c){c="twitter.com/";return b.link("//"+(b[a="search"]("#")?c:a+"."+c+a+"?q=")+b)})}

LICENSE.txt

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
                    Version 2, December 2004

 Copyright (C) 2011 Jed Schmidt <http://jed.is>

 Everyone is permitted to copy and distribute verbatim or modified
 copies of this license document, and changing it is allowed as long
 as the name is changed.

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

  0. You just DO WHAT THE FUCK YOU WANT TO.

package.json

{
  "name": "enlink",
  "keywords": ["twitter", "tweet", "link", "mention", "hashtag"]
}

Awesome work Jed, although I have some changes:

1. It matches email address too, so need \B to indicate a word boundary
2. It contains the @ in the mention URL (which works, but it isn't perfect)

I've made some changes to fix these issues and it comes in at 138 bytes:

function(a){return a.replace(/\B[@#]\w+/g,function(b){return b.link('//twitter.com/'+(b[a='search']('#')?'':a+'?q=%23')+b.substring(1))})}

ha, who tweets email addresses?

(but seriously, thanks! fixed.)

You need to use \B instead of \b. \b matches boundaries where a word and a non-word character met (or vice versa). For example, '[email protected]'.replace(/\b/g,'|') returns |example|@|example|.|com|, making all boundaries visible. In your case, you need it the other way around. There should not be a boundary in front of the @. Hope that helps.