Question

I want to do THIS, just a little bit more complicated:

Lets say, I have an HTML input:

<a href="http://www.example.com" title="Bla @test blubb">Don t break!</a>
Some Twitter Users: @codinghorror, @spolsky, @jarrod_dixon and @blam4c.
You can t reach me at blam4c@example.com.

Is there a good RegEx to replace the twitter username mentions by links to twitter, but leave @example (eMail-Adress at the bottom) AND @test (in the link title, i.e. in HTML tags)?

It probably should also try to not add links inside existing links, i.e. not break this:

<a href="http://www.example.com">Hello @someone there!</a>

My current attempt is to add ">" at the beginning of the string, then use this RegEx:

Search:   />([^<]*s)@([a-z0-9_]+)([s,.!?])/i 
Replace:  >1<a href="http://twitter.com/2">@2</a>3

Then remove the ">" I added in step 1.

But that won t match anything but the "@blam4c". I know WHY it does so, that s not the problem.

I would like to find a solution that finds and replaces all twitter user name mentions without destroying the HTML. Maybe it might even be better to code this without RegEx?

Answer 1

First, keep the angle brackets out of your regexps.

Use a HTML parser and xpath to select the text nodes you are interested in processing, then consider a regexp for matching only @refs in those nodes.

I ll let to other people to try and give a specific answer to the regex part.

Answer 2

I agree with ddaa, there s almost no sane way to attack this without stripping the html links out first.

Presumably you d be starting out with an actual Twitter message, which cannot by definition include any manually entered hyperlinks.

For example, here s how I found this question (the link resolves to this question so don t bother clicking it!)

Some Twitter Users: @codinghorror, @spolsky, @jarrod_dixon and @blam4c. http://bit.ly/2phvZ1

In this case, it s easy:

var msg = "Some Twitter Users: @codinghorror, @spolsky, @jarrod_dixon and @blam4c. http://bit.ly/2phvZ1";

var html = Regex.Replace(msg, "(?<!w)(@(w+))", 
    "<a href="http://twitter.com/$2">$1</a>");

(this might need some tweaking, I d like to test it against a corpus, but it seems correct for the average Twitter message)

As for your more complicated cases (with HTML markup embedded in the tweets), I have no idea. Way too hard for me.

Answer 3

This regexp might work a bit better: /B@([w-]+)/gim

Here s a jsFiddle example of it in action: http://jsfiddle.net/2TQsx/4/

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