An optional PostMessageOptions object is being added to the postMessage() function for 6 of the 7 interfaces where it’s supported, specifically, DedicatedWorkerGlobalScope, Worker, ServiceWorker, ServiceWorker, and Window. This gives the function a similar interface on its definitions and allows it to be extended in the future. Since broadcastChannel.postMessage() doesn't take additional arguments (such as transfer) it is not being changed.
Specification currently under development in a Working Group
Status in Chromium
Enabled by default
Consensus & Standardization
Last updated on 2020-11-09