Expression Library and Patterns in Javascript Custom Controls

Hi there!

It is definitely possible to use both the Expressions library and the Validation Patterns library with JavaScript Custom Controls. The answer to both is yes as long as you are on the latest fixpack for 5.9.

1) Using Expressions

To add expression support to your custom control, use the standard ControlExpression property in your manifest. That’s how you expose an expression-enabled property for your control.

You can find details in the Control-Dojo docs here:
- Manifest Configuration 
- Standard Properties

2) Using Validation Patterns (Design-Time)

For design-time validation, any property on your control can participate in validation by using the validationpattern and validationmessage attributes in the manifest. This lets your custom control properties behave just like built-in controls from a validation perspective.

Docs here:
- Form View Validation

3) Runtime Validation (JavaScript in Your Control)

If you also want runtime validation (i.e., JavaScript logic that runs inside your control’s JS files), you can implement that directly in your control script.

Hope that helps!