Description

MessagePort objects can be transferred to another process such as a worker and can be accessed via events.ports as below, but it's not working now. This PR fixes it.

// Main thread
const worker = new MyWorker()
const channel = new MessageChannel()
worker.postMessage('some-data', [channel.port2]) // <- `channel.port2` is of type `MessagePort` and transferred to the worker.

// Worker thread
self.onmessage = (e) => {
  const port = e.ports[0] // <- The transferred `MessagePort` object should be accessed as `e.ports[i]`, however, it's `undefined` now.
  if (port) {
    port.postMessage("data from worker")
  }
}

Refs:

• https://developer.mozilla.org/en-US/docs/Web/API/MessageChannel
• https://developer.mozilla.org/en-US/docs/Web/API/MessageEvent/ports
• https://github.com/mdn/dom-examples/tree/9a8acd0da2417372655b22d5a0ced768e76deb1c/channel-messaging-basic (sample project)

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