[WebSocket] Add `CloseEvent`

[regseb]

What is the problem this feature will solve?

In Node.js v21 with --experimental-websocket, the CloseEvent class isn't defined. This event is sent to clients using WebSockets when the connection is closed.

What is the feature you are proposing to solve the problem?

Add the CloseEvent class in the global scope (behind --experimental-websocket flags). I found it in undici but it isn't exported. Or add the CloseEvent class next to MessageEvent (directly in Node.js).

What alternatives have you considered?

No response

Related issues

• Adding Websocket support to core #19308
• Add CloseEvent #46880
• lib: enable WebSocket by default #51594
• put ErrorEvent and CloseEvent on global scope undici#2084
• expose websocket in node bundle undici#2217
• expose WebSocket related events in node bundle undici#3167

[github-actions]

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[regseb]

CloseEvent is part of the WebSockets specification. I think we need to keep this issue open if we want Node.js to be compliant with this specification.

[avivkeller]

@nodejs/undici

[mcollina]

This is a actually easy to add.