MessageChannel.messageEventInitInitializer for a Dom_html.messageEvent. All fields are optional; create an empty record with empty_message_event_init and populate the ones you need. The data payload is injected as Js.Unsafe.any; the resulting event is read back at whatever type the caller annotates messageEvent_with_init with.
method ports : messagePort Js_of_ocaml__.Js.t Js_of_ocaml__.Js.js_array
Js_of_ocaml__.Js.t
Js_of_ocaml__.Js.writeonly_prop