Form data and validation
A form with slice captures its named controls under
datadom.formData.<slice> as controls emit events and when
the form submits. The same data is mirrored under the form slice and is
the source of truth for rendering and validation.
The custom-validity expression can return a boolean or a
message string. A false boolean prevents submission; a string makes the
form or control invalid and supplies its validation message. Native and
custom messages are available through datadom.validationState.
See the browser APIs behind these examples in FormData and Constraint validation.
See also
Slice declarations and event bindings