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4GuysFromRolla.com : ASP FAQS : Strings


How can I count the number of substrings in a string?

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Answer: There may be a time when you need to quickly determine the number of substrings instances in a string. For example, an ASPMessageboard.com poster, Anders Liane, wanted to be able to check a user-entered form field and ensure it had fewer than three carraige returns (vbCrLf). [View the Messageboard Post]

VBScript contains a nifty function to determine the position of a particular substring within another string (InStr) (see the FAQ: How can I find the position of a certain character (or substring) within a string?), but InStr, alone, cannot be used to determine how many instances of the substring appear in the string. So.... I wrote my own little function, GetSubstringCount. This function has the following definition:

SubstringCount = GetSubstringCount(SearchString, Substring, CaseSensitive)

GetSubstringCount returns an integer, the count of the number of Substrings found in SearchString. CaseSensitive is a Boolean value specifying whether or not to perform a case or case insensitive choice (use values of True and False, respectively). The code for GetSubstringCount is painfully simple, it's just a couple of lines of code!

Function GetSubstringCount(strToSearch, strToLookFor, bolCaseSensative)
  If bolCaseSensative then
    GetSubstringCount = UBound(split(strToSearch, strToLookFor))
    GetSubstringCount = UBound(split(UCase(strToSearch), UCase(strToLookFor)))
  End If
End Function

You can then use it in a script like:

Function GetSubstringCount(strToSearch, strToLookFor, bolCaseSensative)
  If bolCaseSensative then
    GetSubstringCount = UBound(split(strToSearch, strToLookFor))
    GetSubstringCount = UBound(split(UCase(strToSearch), UCase(strToLookFor)))
  End If
End Function

'How many "t"'s in str?
Dim str, strSubstring
str = "This is a test!"
strSubstring = "t"

Response.Write "There are " & GetSubstringCount(str, "t", False) & " t's in """ & str & """"

The output for the above snippet of code is:
There are 3 t's in "This is a test!"

Neat, eh? To find out how this function works, you need to understand two things: how split works and how UBound works. Fortunately there are FAQs that explain how both of these work!

How can I convert a string into an array? (A FAQ on using split.)
How can I tell the upper or lower bounds of an array? (A FAQ on using UBound.)

I created a live demo that illustrates how to use this function. Be sure to give it a try out, play with it, have fun!

There is even a third way to accomplish this (which I think is a very clever way) - using VBScript's Replace function like so:

SubstringCount = Len(Replace(str, strSubstring, strSubstring & "*")) - Len(strSubstring)

This method was shared by Jan Meulepas in this ASPMessageboard.com post...

Happy Programming!

FAQ posted by Scott Mitchell at 2/8/2001 1:47:26 AM to the Strings category. This FAQ has been viewed 63,085 times.

Do you have a FAQ you'd like to suggest? Suggestions? Comments? If so, send it in! Also, if you'd like to be a FAQ Admin (creating/editing FAQs), let me know! If you are looking for other FAQs, be sure to check out the 4Guys FAQ and Commonly Asked Messageboard Questions!

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Last computed at 9/17/2007 3:22:00 AM

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