ISBN Functions

fnisbn13

This Classic ASP function will convert your old 10 digit ISBN numbers to the new ISBN-13 standard. It requires one parameter: either a 9 or 10 digit ISBN-10.

function fnisbn13(strparam1)
	vari=0
	varv=0
	varn=0
	varc=""
	varResult=""
	vars12=""
	varISBN10=strparam1
	varlen=len(varISBN10)
	if varlen<9 or varlen>10 then
		varResult="ERROR"
	else
		vars12="978"+left(varISBN10,9)
		for vari=0 to 11
			if varResult="" then
				varc=mid(vars12,vari+1,1)
				if varc>="0" and varc<="9" then
					varv=varc-0
					if vari mod 2<>0 then varv=3*varv
					varn=varn+varv
				end if
			else
				varResult="ERROR"
			end if
		next
		if varResult="" then
			varn=varn mod 10
			if varn<>0 then varn=10-varn
			varResult=vars12 & varn
		end if
	end if
	fnisbn13=varResult
end function