ExtendableMessageEventInit
fun ExtendableMessageEventInit(
data: Any? = undefined,
origin: String? = undefined,
lastEventId: String? = undefined,
source: UnionClientOrMessagePortOrServiceWorker? = undefined,
ports: Array<MessagePort>? = undefined,
bubbles: Boolean? = false,
cancelable: Boolean? = false,
composed: Boolean? = false
): ExtendableMessageEventInit