VBScript in a Nutshell, 2nd Edition

Name

Asc, AscB, AscW Functions

Syntax

Asc(string)
AscB(string)
AscW(string)

string

Use: Required

Data Type: String

Any expression that evaluates to a string.

Return Value

An integer that represents the character code of the first character of the string.

Description

Returns the ANSI (in the case of Asc) or Unicode (in the case of AscW ) character code that represents the first character of the string passed to it. All other characters in the string are ignored. The AscB function returns the first byte of a string.

Rules at a Glance

• The string expression passed to the function must contain at least one character, or a runtime error (either “Invalid use of Null” or “Invalid procedure call or argument”) is generated.

• Only the first character of the string is evaluated by Asc, AscB, and AscW.

• Use the AscW function to return the Unicode character of the first character of a string.

• Use the AscB function to return the first byte of a string containing byte data.

Example

<%
Dim sChars
Dim iCharCode
   
sChars = Request.Form("chars")
If Len(sChars) > 0 Then
    CharCode = Asc(sChars)
    If iCharCode >= 97 And iCharCode <= 122 Then
        Response.Write "The first character must be uppercase"
    Else
        Response.Write iCharCode 
    End If
End If
%>

Programming Tips and Gotchas

• Always check that the string you are passing to the function contains at least one character using the Len function, as the following example shows:

  If Len(sMyString) > 0 Then iCharCode = Asc(sMyString) Else Response.Write "Cannot process a zero-length string" ...