While working on an ASP ticket system today that required regular expressions, I came up with a couple of useful regular expression patterns that may save people a few hours of thinking time.
Matching and extracting a string
Problem: I have the following chunk of arbitrary text and I want to extract the order number prefixed “ORD_”:
The quick brown fox... ORD_1012345678 ...jumped over the lazy dog
Solution: ORD_[a-zA-Z0-9_-]*
What is going on? Well, quite simply the regular expression engine is being asked to match the first three letters “ORD” followed by an underscore “_”. It then requires a series (*) of letters, numbers, underscores or dashes (but nothing else). Therefore, once the regular expression engine has found the order number “ORD_1012345678″ and then it comes to a whitespace, new line, period or whatever - it stops parsing.
ASP VBScript Code:
Set regEx = New RegExp
With regEx
.Pattern = "ORD_[a-zA-Z0-9_-]*"
.IgnoreCase = true
.Global = false
End With
set matches = regEx.Execute(text)
if matches.count > 0 then
result = matches.item(0).value
end if
The string “ORD_1012345678″, extracted from the chunk of text, will be stored in the variable “result”
A very similar version of string extraction
Problem: I have the following chunk of arbitrary text and I want to extract the ID number in square brackets (prefixed “[#”):
The quick brown fox jumped over the lazy dog [#101234-56789]
Solution: \[#([a-zA-Z0-9_-]*)
What is going on? In a similar way to the first one, this regular expression match pattern is asking for a square bracket followed by a hash “[#” - but because the opening square bracket is a reserved character (used to define sets), we have to escape it with a backwards slash before hand. We then surround the series of allowed characters with parenthesis ( ) which groups the match as a “sub match”.
ASP VBScript Code:
Set regEx = New RegExp
With regEx
.Pattern = "\[#([a-zA-Z0-9_-]*)"
.IgnoreCase = true
.Global = false
End With
set matches = regEx.Execute(text)
if matches.count > 0 then
result = matches(0).subMatches(0)
end if
The ID number “101234-56789″ will be stored in “result”
The important difference to note in this code is the use of “subMatches(0)” which returns the first match found in the brackets.
Stripping HTML tags
This function can be used to strip HTML tags from a string. It is very similar to the PHP function strip_tags(); but this one is not as advanced (yet).
A more advanced version is now available here 
Let’s just jump straight to the code, you don’t really need to know what is going on (you can probably guess anyway)…
ASP VBScript Code:
function stripTags(strHTML)
dim regEx
Set regEx = New RegExp
With regEx
.Pattern = "< (.|\n)+?>"
.IgnoreCase = true
.Global = false
End With
stripTags = regEx.replace(strHTML, "")
end function
Trimming unwanted whitespace
If you want to trim unwanted whitespace from a string, e.g: turning “Text[space]spaced[space]normally[space][space][space]or[space][space]not?” into: “Text[space]spaced[space]normally[space]or[space]not?” use the following method:
function trimWhitespace(strIn, singleSpacing)
dim regEx
Set regEx = New RegExp
With regEx
.Pattern = "\s+"
.IgnoreCase = true
.Global = false
End With
if singleSpacing then
space = " "
else
space = ""
end if
trimWhitespace = regEx.replace(strIn, space)
end function
When set to false, the second parameter “singleSpacing” will simply remove all whitespaces from a string, giving: “Textspacednormallyornot?”
I hope the above examples help someone!
You may find the following websites useful, I certainly did!