Regular Expressions in Classic ASP
The VBScript RegExp object can test whether a string matches a required pattern. In Classic ASP this is useful for validating the shape of values such as user IDs or email addresses before further processing.
Pattern validation is only one layer of security. It does not replace prepared/parameterized database commands, output encoding, authorization checks, or business-rule validation.
Create a RegExp object
Dim re
Set re = New RegExp
re.IgnoreCase = True
re.Global = FalseSet Pattern to the rule you want to test, then call Test(value). For validation, anchoring the expression with ^ and $ usually ensures the whole value is checked rather than just a matching substring.
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What regular expressions are good for
- Restricting a user ID to an expected character set and length.
- Checking that a value has a plausible email-address format.
- Recognizing structured codes such as ZIP/postal formats when the application has a clearly defined rule.
Do not use a very restrictive pattern when valid real-world input is more varied than the pattern allows. Validate only what the application genuinely requires.
Test a complete user-ID pattern
Dim re
Set re = New RegExp
re.Pattern = "^[A-Za-z0-9]{3,8}$"
re.IgnoreCase = True
Response.Write re.Test("A23")Output:
TrueThe anchors force the whole string to match. Test() returns True or False.
Regex validation is one layer
Anchor patterns with ^ and $ when the full input must match. Regular expressions do not replace authorization checks, parameterized database queries or safe HTML output.
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Subhendu Mohapatra
Author & Instructor at plus2net
I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.
