Description

The form-associated custom elements APIs enable custom elements to participate in form submission and validation lifecycles.

This agreed upon spec is not fully delivered cross browser. Following the Web Platform Test link below, you will find the it is currently missing in Safari and suffers from a number of failures in Firefox.

Rationale

• Enable custom elements to participate in form submission by adding a value to the FormData object, adding to the HTMLFormElement.prototype.elements object and in other submission formats.
• Enables custom elements to participate in the form validation lifecycle by providing APIs similar to and building on top of the constraint validation APIs.

Specification

https://html.spec.whatwg.org/multipage/custom-elements.html#form-associated-custom-elements

Tests

https://github.com/web-platform-tests/wpt/tree/master/custom-elements/form-associated