Validating form behavior
The redirect URL must be absolute HTTPS URL otherwise AMP will throw an error and redirection won't happen.
Known Issue: Due to an issue in Safari i OS redirecting to deep linked URLs (URLs that would actually end up opening a native app) might fail when the AMP document is embedded. provide polyfills for behaviors and functionality missing from some browsers or being implemented in the next version of CSS.
For details on valid inputs and fields, see amp-form rules in the AMP validator specification. This allows you to trigger the form submission on a specific action, for example, tapping a link, or submitting a form on input change.
You can read more about Actions and Events in AMP in the spec.
For “cancel” type buttons, the validation is normally skipped entirely.
Form validation takes two forms: field-level validation, pertaining to the value of an individual field, and form-level validation, pertaining to the form as a whole.
Using the Behaviors property you can add behaviors that attached to the Control and can execute code when events of that control are raised.
Documentation: Introduction to Behaviors Example Use Case: Apply validation rules to an Entry control. We can use the Is Valid property to bind to something just as a Button Is Enabled Property or similar to stop users from progressing forward without meeting the forms requirements.
Take the following basic form: If you have focus in the textbox and hit enter, the form will be submitted automatically.This behavior is consistent across all browsers and is known as implicit submission. Implicit submission is vital to assistive technologies and impaired users that cannot use a mouse at all.From the HTML5 specification: The spec strongly encourages browsers to allow implicit submission; they all do.Browsers will send the request in the background using Fetch API when available and fallback to XMLHttp Request API for older browsers.The value for (Relaxing some of these rules might be reconsidered in the future - please let us know if you require these and provide use cases).