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I would like to understand the exact difference between ws.close() and ws.terminate().

I don't find the doc very clear, about it because as I tested them, they behave exacly the same. Both trigger "close" event on the other side if open.

so when to use one instead of the other?

thank you.

Use ws.close() when you want to close the connection gracefully and/or want to use a specific close code/reason. This implements the close handshake.

Use ws.terminate() to shut down the connection immediately.

This may not tell the complete story.
I found that ws.close() may still execute signal handlers 30 seconds after close() if the network connection is unavailable, while ws.terminate() did not show this behaviour.

During a change of network (e.g. from wired to wireless), when I create a new WebSocket() and registered all signal handlers (onopen/onclose/onerror), I was struggling that the new connection went up, but was consistently receiving 1006/onclose events from the previous socket, which is confusing, but also correct behaviour.

Please also refer to #891

My question is highly related and dont want to open an issue, super appreciated if you can clarify something, I noticed in the source code that error triggers a close

Are error and close always triggered together

Are there situations where error can be triggered without close and vice-versa?

I am trying to call a reconnect method when the connection errors out unless I explicitly disconnected it, having some problems with things happening twice

Are error and close always triggered together

Not always, there might be buffered data and until all data is read the 'close' event is not emitted. You always get a 'close' event after an 'error' event.

Are there situations where error can be triggered without close and vice-versa?

'close' can be emitted without 'error' (clean close).

I am trying to call a reconnect method when the connection errors out unless I explicitly disconnected it, having some problems with things happening twice

Use the 'close' event and an heartbeat system based ping/pong frame where the connection is terminated if no ping is received within an expected amount of time.

I looked at the code and I gather it emits close if the state is CONNECTING but not otherwise. In the code below abortHandshake() does emit close but then you have this._socket.destroy() which doesn't trickle up to the WebSocket instance ... what am I missing?

  terminate() {
    if (this.readyState === WebSocket.CLOSED) return;
    if (this.readyState === WebSocket.CONNECTING) {
      const msg = 'WebSocket was closed before the connection was established';
      return abortHandshake(this, this._req, msg);
    if (this._socket) {
      this.readyState = WebSocket.CLOSING;
      this._socket.destroy();
          
@lpinca Does terminate inform the other side of what is happening? I am trying to write a test where the client disconnects un-grafully (to test my ping pong handler and kicker) and I'm wondering if terminate can be used for this, from what I see it triggers the close event on the server side (which is not what I want).
Use ws.terminate() to shut down the connection immediately.
This sounds like it's just "faster" than .close(). Could you maybe edit your post to advise more caution?
What it really does is not a clean shutdown, but rather it simply drops the connection. One should only do this in case of an error. There is no closing handshake, neither on the websocket nor the tcp level, the other end of the connection will be oblivious of the dropped connection. (They will only run into a tcp timeout after (if!) attempting to send something).
More details: https://stackoverflow.com/a/74081838/1048572?when-is-it-preferable-to-use-ws-terminate-vs-ws-close