This event is emitted before a form is being validated.
The form that is being validated.
The form parameters that will be sent as the form's request payload.
Listeners may inspect and modify params before they are sent.
The form fields that triggered this validation pass.
When multiple fields are validating within the same task, Unpoly will make a single validation request with multiple targets.
An object with render options for the fragment update that will show the validation results.
Listeners may inspect and modify these options.
Prevents the validation request from being sent to the server.
