<!-- verify.js -->

    // invoke from onSubmit() event handler
    function verify(form)
    {
        var msg = "Your form could not be submitted due to the following:\n\n";
        var errors = "";
        
        for(var i = 0; i < form.length; i++)
        {
            var e = form.elements[i];
            
            if((e.type == "text") || (e.type == "textarea"))
            {
                if(!e.optional)
                {
                    // e is a non-optional text field
                    // check if field is empty
                    if(isEmpty(e.value))
                    {
                        errors += "Required field \"" + e.description + "\" is empty\n";
                        continue;
                    }
                }
                
                // check for fields that are supposed to be numeric
                if(((e.numeric) || (e.min != null) || (e.max != null)) && (!isBlank(e.value)))
                {	
                    var v = parseFloat(e.value);
                    if(isNaN(v) ||
                        ((e.min != null) && (v < e.min)) ||
                        ((e.max != null) && (v > e.max)))
                    {
                        errors += "The field \"" + e.description + "\" must be a number";
                        if(e.min != null)
                            errors += " greater than " + e.min;
                        if(e.max != null && e.min != null)
                            errors += " and less than " + e.max;
                        else if(e.max != null)
                            errors += " less than " + e.max;
                        
                        errors += "\n";
                    }
                }

		  // check for fields that are supposed to be email addresses
		  if((e.email) && (!isBlank(e.value)))
		  {
			if(!isEmail(e.value)) 
			{
				errors += "The field \"" + e.description + "\" must be an email address\n";
			}
		  }

            } // end if text field
        } // end for(form.length)
        
        if(!errors) 
        {
            return true;
        }
        else
        {
            alert(msg + errors);
            return false;
        }
        
    }
    
    // utility function; returns true if string contains only whitespace characters
    function isBlank(s)
    {
        for(var i = 0; i < s.length; i++)
        {
            var c = s.charAt(i);
            if((c != ' ') && (c != '\n') && (c != '\t')) return false;
        }
        return true;
    }

    // utility function; returns true if input value is empty
    function isEmpty(v)
    {
	 if((v == null) || (v == "") || isBlank(v))
	     return true;
	 else
	     return false;
    }

    // utility function; returns true is string has format x@*
    function isEmail(s)
    {
	 for(var i = 1; i < s.length; i++)
	 {
	    var c = s.charAt(i);
	    if(c == '@') return true;
	 }
	 return false;
    }