// A utility function that returns true if a 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;
}

// This is the function that performs form verification. It is invoked
// from the onsubmit event handler. The handler should return whatever
// value this function returns.
function verify(f) {
    var msg;
    var empty_fields = "";
    var errors = "";

    for(var i = 0; i < f.length; i++) {
        var e = f.elements[i];
        if (((e.type == "text") || (e.type == "textarea")) && !e.optional) {
            // first check if the field is empty
            if ((e.value == null) || (e.value == "") || isblank(e.value)) {
                empty_fields += "          " + e.name + "\n";
                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 " + 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";
                }
            }
        }
    }
         
         // Check that the Category is selected
		if (f.Category.selectedIndex == 0) {
			errors += 'Please select a Recipe Category.\n';
        }
		
		// Check that the Recipe Type is selected
		if (f.RecipeType.selectedIndex == 0) {
			errors += 'Please select a Recipe Type.\n';
		}
		
		// Check that the Submitter's Type is selected
		if (f.SubmitType.selectedIndex == 0) {
			errors += 'Please choose from the dropdown under the Submitter\'s Name.\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  = "______________________________________________________\n\n";
    msg += "The form was not submitted because of the following error(s).\n";
    msg += "Please correct these error(s) and re-submit.\n";
    msg += "______________________________________________________\n\n";

    if (empty_fields) {
        msg += "- The following required field(s) are empty:\n" + empty_fields + "\n";
        if (errors) {
                msg += "\n";
                msg += "______________________________________________________\n\n";
                msg += "The following fields have errors.  Please correct.\n";
        }
    }
    msg += errors;
    alert(msg);
    return false;
}