// This is the function that performs form verification.
// Checks any text or text area element against pre-defined 
// 'optional', 'max' and 'min' properties.
// Doesn't do radio buttons or check boxes.
// NB - 'max' and 'min' refer to NUMERIC values.
// NB - calls stripPrefixAndUnderscore to remove first 3 chars of field name - eg txtSurname -> Surname
function verify(f)
{
    var msg;
    var empty_fields = "";
    var errors = "";
    // Loop through the elements of the form, looking for all
    // text and textarea elements that don't have an "optional" property
    // defined. Then, check for fields that are empty and make a list of them.
    // Also, if any of these elements have a "min" or a "max" property defined,
    // then verify that they are numbers and that they are in the right range.
    // Put together error messages for fields that are wrong.
    for(var i = 0; i < f.length; i++) {
        var e = f.elements[i];
        if (((e.type == "text") || (e.type == "textarea") || (e.type == "password")) && !e.optional) {
            // first check if the field is empty
            if ((e.value == null) || (e.value == "") || isblank(e.value)) {
                empty_fields += "\n          " + stripPrefixAndUnderscore(e.name,3);
                continue;
            }
            // Now check for fields that are supposed to be numeric.
            if (e.numeric || (e.min != null) || (e.max != null)) {
                var v = parseFloat(e.value);
                if (isNaN(v) ||
                    ((e.min != null) && (v < e.min)) ||
                    ((e.max != null) && (v > e.max))) {
                    errors += "- The field " + stripPrefixAndUnderscore(e.name) + " must be a number";
                    if (e.min != null)
                        errors += " that is greater than " + e.min;
                    if (e.max != null && e.min != null)
                        errors += " and less than " + e.max;
                    else if (e.max != null)
                        errors += " that is less than " + e.max;
                    errors += ".\n";
                }
            }
        }
    }
    // Now, if there were any errors, display the messages, and
    // return false to prevent the form from being submitted.
    // Otherwise return true.
    if (!empty_fields && !errors) return true;
    msg =  "";
   // msg  = "______________________________________________________\n\n"
   // msg += "Your form isn't quite complete yet.\n";
   // msg += "Please sort out the issues below and try again:\n";
   // msg += "______________________________________________________\n\n"
    if (empty_fields) {
        msg += "- The following required field(s) are empty:"
                + empty_fields + "\n";
        if (errors) msg += "\n";
    }
    msg += errors;
    alert(msg);
    return false;
}

// Removes first chars from string
// s = string to remove prefix from, n is no of chars to strip from string
function stripPrefixAndUnderscore(s, n)
{
	noRemove = n;
	stripped = s.substring(n,s.length);
	str = stripped.replace(/_/, " ");
	
	return str;
}