Add support to addEventListener for object containing handleEvent

[mattrunyon]

Is there an existing issue for this?

• I've searched for any related issues and avoided creating a duplicate issue.

Description

The Node EventTarget class supports both a function as the listener, and an object with a handleEvent function. I.e. addEventListener(name: string, listener: Function | { handleEvent: Function })

Node docs

I've read through #1818 and see it is unlikely this package will use the native Node EventTarget. I think it would be helpful to add this to the EventTarget shim to more closely match the Node implementation.

My use case is generated code which I don't control that is generating addEventListener(name, { handleEvent: () => {}). Valid in the browser, but breaks with Node using ws

I am currently working around by using the following. In an implementation in this package, it might be simpler to use handler.handleEvent.call(handler) to keep the this context

class CustomWs extends ws {
  static boundHandlerMap = new Map();

  addEventListener(name, handler, ...rest) {
    if (typeof handler.handleEvent === 'function') {
      const boundHandler = handler.handleEvent.bind(handler);
      boundHandlerMap.set(handler, boundHandler);
      super.addEventListener(name, boundHandler, ...rest);
    } else {
      super.addEventListener(name, handler, ...rest);
    }
  }

  removeEventListener(name, handler, ...rest) {
    if (typeof handler.handleEvent === 'function') {
      const boundHandler = boundHandlerMap.get(handler, boundHandler);
      super.removeEventListener(name, boundHandler, ...rest);
    } else {
      super.removeEventListener(name, handler, ...rest);
    }
  }
}

ws version

8.10.0

Node.js Version

16.17.0

System

OS: macOS 12.3.1

Expected result

socket.addEventListener('message', { handleEvent: e => console.log(e) }) should work identically to socket.addEventListener('message', e => console.log(e))

Actual result

The handleEvent object does not get added and the listener is never called

Attachments

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