Understanding the '-- None --' Value in ServiceNow Select Boxes

When using ServiceNow, developers and administrators often encounter select boxes with an option labeled '-- None --'. Many users wonder what actual value this option holds internally. This article clarifies the exact meaning of the '-- None --' value, addresses common misconceptions, and offers practical tips for correct implementation and troubleshooting.

What Does '-- None --' Mean in a ServiceNow Select Box?

In ServiceNow, the '-- None --' option represents a blank or empty value. Internally, it is treated as an empty string (''). Contrary to common assumptions, it does not carry any hidden numerical or textual value—it's simply an absence of a selected value.

Understanding that '-- None --' equates to a blank or empty string ('') is crucial when writing client scripts or setting conditions.

Common Misconceptions About '-- None --'

Some users mistakenly assume '-- None --' might correspond to a numerical value, such as '0' or '-1'. However, it consistently translates internally as a blank (''). Misunderstanding this can lead to incorrect logic in your scripts, causing unexpected behaviors or errors.

How to Check and Troubleshoot the '-- None --' Value

Here’s how you can accurately detect if '-- None --' is selected using a client script in ServiceNow:

function onChange(control, oldValue, newValue, isLoading, isTemplate) {
   if (isLoading || newValue === '') {
      return;
   }

   // Your custom logic here
}

By using newValue === '', you clearly differentiate the '-- None --' option from other potential selections.

Practical Example

Here's a practical scenario illustrating how you can clear or set a default value based on the selection:

function onChange(control, oldValue, newValue, isLoading, isTemplate) {
   if (isLoading) {
      return;
   }

   if (newValue === '') {
      // Clear or reset another field if '-- None --' is selected
      g_form.clearValue('another_field');
   } else {
      // Set a default value if another selection is made
      g_form.setValue('another_field', 'Default Value');
   }
}

Alternative Approaches

If you want to explicitly set a field's default option as '-- None --', you can programmatically add it as follows:

g_form.addOption('field_name', '', '-- None --');

Conclusion and Next Steps

Clearly recognizing that the '-- None --' option in ServiceNow is effectively a blank value ('') makes it easier to handle form conditions, scripting, and data validation.

Next, consider these actions:

• Regularly test your scripts across various forms to ensure accurate handling of the '-- None --' selection.

• Refine existing client scripts by explicitly checking for blank values ('').

• Familiarize yourself with alternative approaches for handling default selections in select boxes.

Applying these insights will simplify your scripting tasks and enhance the overall usability of your ServiceNow implementation.