Regex to replace domain within links that are not images

Question

Need to replace a domain name on all the links on the page that are not images or pdf files. This would be a full html page received through a proxy service.

Example:
<a href="http://www.test.com/bla/bla">test</a><a href="/bla/bla"><img src="http://www.test.com" /><a href="http://www.test.com/test.pdf">pdf</a>
<a href="http://www.test.com/bla/bla/bla">test1</a>

Result:
<a href="http://www.newdomain.com/bla/bla">test</a><a href="/bla/bla"><img src="http://www.test.com" /><a href="http://www.test.com/test.pdf">pdf</a>
<a href="http://www.newdomain.com/bla/bla/bla">test1</a>

Can you give a few examples of the input (url) and the output (change url). — Richard Nienaber, Mar 17 '10 at 06:06
its difficult to do with a single regex - use a dom parser - see my updated answer. — Amarghosh, Mar 17 '10 at 08:00

score 2 · Answer 1 · edited May 23 '17 at 10:32

2

If you are using .NET, I strongly suggest you to use HTML Agility Pack Direct parsing using regex can be very error prone. This questions is also similar to the post below.

What regex should I use to remove links from HTML code in C#?

edited May 23 '17 at 10:32

Community

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answered Mar 17 '10 at 06:07

Fadrian Sudaman

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KJ Saxena · Accepted Answer · 2010-03-17T06:19:16.157

0

If the domain is http://www.example.com, the following should do the trick:

/http:\/\/www\.example\.com\S*(?!pdf|jpg|png|gif)\s/

This uses a negative lookahead to ensure that the regex matches a string only if the string does not contain pdf,png,jpg or gif at the specified position.

edited Mar 17 '10 at 06:19

answered Mar 17 '10 at 06:13

KJ Saxena

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Remove the trailing \s if your links do not end in a whitespace. Use this: /http:\/\/www\.example\.com\S*(?!pdf|jpg|png|gif)/ – KJ Saxena Mar 17 '10 at 06:38
tried running that against an example above, it replaces all the urls – pbcomm Mar 17 '10 at 07:38

Amarghosh · Answer 3 · 2010-03-17T07:56:49.223

If none of your pdf urls have query parameters (like a.pdf?asd=12), the following code will work. It replaces only absolute and root-relative urls.

var links = document.getElementsByTagName("a");
var len = links.length;
var newDomain = "http://mydomain.com";
/**
 * Match absolute urls (starting with http) 
 * and root relative urls (starting with a `/`)
 * Does not match relative urls like "subfolder/anotherpage.html"
 * */
var regex = new RegExp("^(?:https?://[^/]+)?(/.*)$", "i");
//uncomment next line if you want to replace only absolute urls
//regex = new RegExp("^https?://[^/]+(/.*)$", "i");
for(var i = 0; i < len; i++)
{
  var link = links.item(i);
  var href = link.getAttribute("href");
  if(!href) //in case of named anchors
    continue;
  if(href.match(/\.pdf$/i)) //if pdf
    continue;
  href = href.replace(regex, newDomain + "$1");
  link.setAttribute("href", href);
}

Regex to replace domain within links that are not images

3 Answers3