How to read text from a textbox and make some of them a link?

I will show the problem with a example.

There is some text in the textbox such here:

Hi! this is a example [lnk]text[/lnk]

When i push the submit button and publish this text, the word in the [lnk] and [/lnk] tags must be a link like this www.mysite.com?link=text.

How do I make it easily with javascript or jquery?

Note: I'm not so good about javascript.

From stackoverflow

• This will do the javascript for you - not sure if you need to do anything special for asp.net

  <form onsubmit="return doLinks(this.elements['links']);">
  <textarea name="links" rows="20" cols="80"></textarea>
  <input type="submit">
  </form>
  
  <script type="text/javascript">
  
  function doLinks(elm)
  {
      var matches = elm.value.match(/\[link\](.*?)\[\/link\]/gi);
      for (var i = 0; i < matches.length; i++)
      {
       var url = 'http://www.mysite.com/?link=' + encodeURIComponent(matches[i].substring(6, matches[i].length - 7));
       elm.value = elm.value.replace(matches[i], url);
      }
  
      return true;
  }
  
  </script>