How can I clean HTML tags out of a ColdFusion string?

Question

I am looking for a quick way to parse HTML tags out of a Coldfusion string. We are pulling in an RSS feed that that could potentially have anything in it. We are then doing some manipulation of the information and then spitting it back out to another place. Currently we are doing this with a regular expression. Is there a better way to do this?

<cfloop from="1" to="#ArrayLen(myFeed.item)#" index="i">
  <cfset myFeed.item[i].description.value = 
   REReplaceNoCase(myFeed.item[i].description.value, '<(.|\n)*?>', '', 'ALL')>
</cfloop>

We are using Coldfusion 8.

Answer 1

The best way is usually to coerce < to < and > to >. This way you aren't making assumptions about the nature of the message. Somebody may be talking about <tags> or trying to be <<expressive>> or describing a keystroke <Ctrl>+C or using maths 1 < x > 3. Even smilies could trigger the regex <8P X>

<cfloop from="1" to="#ArrayLen(myFeed.item)#" index="i">
    <cfset myFeed.item[i].description.value = ReplaceList(myFeed.item[i].description.value, '<,>', '&lt;,&gt;')>
</cfloop>

Answer 2

HTML is not a Regular language, so using Regular expressions on (uncontrolled) HTML is something that should be done with great care (if at all).

Consider, for example, the following valid segment of HTML:

<img src="boat.jpg" alt="a boat" title="My boat is > everything! I <3 my boat!">

You'll note how the syntax highlighter is choking on that - as will the existing regex that has been offered.

Unless you can be certain that the string you are processing will not contain HTML code similar to the above, you should avoid making assumptions/compromise, which a single/pure regex route would force you to do.

(Note: The same problem applies to the suggested char-by-char method too.)

To solve your problem, you should use a DOM parser to parse your string into a HTML object, looping through each element and converting to text.

If you have valid XHTML then you can use CF's XmlParse() to produce the object which you can then loop though. If it might be non-XML HTML then there's no built-in option with CF8, so you'll have to investigate options in Java/etc.

Answer 3

cflib is your friend: stripHTML