CFLib.org – Common Function Library Project

Description:
Checks to to see if value is a valid ISBN.

Return Values:
Returns a boolean.

Example:

<cfoutput>
#isISBN("013152447X")#
</cfoutput>

Parameters:

Full UDF Source:

/**
 * Checks to to see if value is a valid ISBN.
 * 
 * @param isbn      ISBN string to check. (Required)
 * @return Returns a boolean. 
 * @author Alex (axs@arbornet.org) 
 * @version 1, May 16, 2002 
 */
function IsISBN(isbn)  {
     var total       = 0;
      var test        = 0;
    var check_digit = 0;
    var i = 1;
    
    if (len(isbn) neq  10) return false;
    
    test = left(isbn,9);
    check_digit = right(isbn,1);
    
    if (NOT isnumeric(test)) return false;
    
    for ( i = 1; i lt 10; i=i+1) {
        total = total + (Mid(isbn, i, 1) * i);
    }

    test = total mod 11; 

    if (test eq 10) test = "X";
            
    if (test eq check_digit) return true;
    else return false;
}