Asp > Strings

Credit Card Validation - Validates a credit card string

Credit Card Validation - Validates a credit card string

<SCRIPT LANGUAGE="VBScript" RUNAT=SERVER>

Function Luhn(s) 
Dim i, iOdd, iEven, sInv, iNum

i = 1
iOdd = 0
iEven = 0
sInv = StrReverse(s)
Do While (i<=Len(sInv))
If Odd(i) Then
iOdd = iOdd + CByte(Mid(sInv, i, 1))
Else
iNum = 2 * CByte(Mid(sInv, i, 1))
If (iNum > 9) Then
iEven = iEven + 1 + (iNum - 10)
Else
iEven = iEven + iNum
End If
End If
i = i + 1
Loop
Luhn = (i>1) And ((iOdd + iEven) Mod 10 = 0)
End Function

Function IsMaster(s) 
IsMaster = IsLen(s, 16) And IInside(CLng(Left(s, 2)), 51, 55) 
End Function

Function IsVISA(s) 
IsVisa = IsPrefix(s, "4") And (IsLen(s, 13) Or IsLen(s, 16))
End Function

Function IsAmex(s) 
IsAmex = IsLen(s, 15) And (IsPrefix(s, "34") Or IsPrefix(s, "37"))
End Function

Function IsDiners(s) 
IsDiners = IsLen(s, 14) And (IsPrefix(s, "36") Or _
IsPrefix(s, "38") Or IInside(CLng(Left(s, 3)), 300, 305))
End Function

Function IsDiscover(s)
IsDiscover = IsLen(s, 16) And IsPrefix(s, "6011")
End Function

Function IsRoute(s) 
IsRoute = IsLen(s, 15) And (IsPrefix(s, "2014") Or _
IsPrefix(s, "2049"))
End Function

Function IsJCB(s) 
IsJCB = (IsLen(s, 15) And (IsPrefix(s, "2131") Or _
IsPrefix(s, "1800")) Or (IsLen(s, 16) And _
IsPrefix(s, "3")))
End Function

' This routine checks for a valid credit card number, according
' to the prefixes and lengths below, and to Luhn's algorithm.
'
' Card Type Prefix Length
'
' MasterCard 51-55 16
' VISA 4 13, 16
' American Express 34, 37 15
' Diner's Club 300-305, 36, 38 14
' Carte Blanche 300-305, 36, 38 14
' Discover 6011 16
' enRoute 2014, 2049 15
' JCB 3 16
' JCB 2131, 1800 15

Function IsCardNumber(sCard, ccType)
Dim ccMin, ccMax, minLen, maxLen, result, ccMaster,_
ccVISA, ccAmex, ccDiners, ccCarteB, ccDiscover,_
ccenRoute, ccJCB

ccMin = 0
ccMax = 7
minLen = 13
maxLen = 16
result = False
sCard = Trim(sCard)

ccMaster = 0
ccVISA = 1
ccAmex = 2
ccDiners = 3
ccCarteB = 4
ccDiscover = 5
ccenRoute = 6
ccJCB = 7

If (IInside(ccType, ccMin, ccMax)) Then
If (IInside(Len(sCard), minLen, maxLen)) Then
Select Case ccType
Case ccMaster
result = IsMaster(sCard)
Case ccVISA
result = IsVISA(sCard)
Case ccAmex
result = IsAmex(sCard) 
Case ccDiners
result = IsDiners(sCard) 
Case ccCarteB
result = IsDiners(sCard) 
Case ccDiscover
result = IsDiscover(sCard) 
Case ccenRoute
result = IsRoute(sCard) 
Case ccJCB
result = IsJCB(sCard) 
End Select
End If
End If

If result Then
result = Luhn(sCard)
End If

IsCardNumber = result
End Function

</SCRIPT>