Utilizing Regular Expressions, Part 3

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Read Part 2
Read Part 1

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In Part 2 we discussed how to use regular expressions to match character classes and pattern repetition. In this part, we'll look at the Replace method of the RegExp object and some finish the article off with a discussion on some of the more advanced uses of regular expressions.

The Replace Method
If you're new to regular expressions, chances are you've always relied on the standard VBScript Replace function to replace certain substrings with other substrings. While the Replace function is easy to use, it lacks the power offered by the Replace method of the regular expression object. For example, imagine that you wanted to replace a number of offensive words in a string with less offensive variations. As we discussed earlier in this article, using the Replace function can lead to some headaches. For example, if we wished to replace all instances of "hell" with "heck" using the Replace function, we'd blindly turn "Hello" into "Hecko".

Using regular expressions, however, we can search for the word "hell" by using the special word boundary symbol. The following code snippet will replace particular words with other words (and can easily be adapted to provide a censorship type system on your site):

Dim str ' some string that needs to have certain words ' replaced with other words Dim objRegExp Set objRegExp = New RegExp objRegExp.IgnoreCase = True objRegExp.Global = True 'Replace all instances of Apache with IIS objRegExp.Pattern = "\bApache\b" str = objRegExp.Replace(str, "IIS") 'Repalce all instances of Perl with ASP objRegExp.Pattern = "\bPerl\b" str = objRegExp.Replace(str, "ASP") Set objRegExp = Nothing 'Clean up!

Note that the Replace method takes two parameters: the first is the string to search; the second is the text to replace any matches with. The Replace method returns the modified string.

Advanced Uses of Regular Expressions
One of the best uses of regular expressions is for server-side form validation. I have not been able to find many articles on server-side form validation using regular expression using VBScript. Those only article I found was one here on 4Guys:

• Validate What? Using Regular Expression to Validate Input
  

I did, however, find a number of articles on client-side validation with regular expression and server-side validation with regular expression.

• Validating Email Addresses Using JScript and Regular Expression
  
• A Library of Regular Expression for Form Validation
  
• Validation Made Simple with JScript Regular Expressions

There are, of course, other uses for regular expression. If you have some good, practical uses of regular expression, and would like to share them with the 4Guys audience, please send me your ideas!

Happy Programming!

Read Part 2

Read Part 1