Websocket download not work in firefox

[AlwaysNoobCoder]

const fileStream = createWriteStream("users.csv", {
  size: 164224, // (optional filesize) Will show progress
  writableStrategy: undefined, // (optional)
  readableStrategy: undefined, // (optional)
})
const writer = fileStream.getWriter()

const ws = new WebSocket("wss://portal-local.itps.xxx.com:3000/ws/export/sea/users")

ws.binaryType = "arraybuffer"

ws.onopen = () => {
  console.log("websocket connected")
  ws.send("{}")
}
ws.onmessage =  (event) => {
  // console.log("websocket message", event)
   writer.write(new Uint8Array(event.data))
}
ws.onclose =  (event) => {
  console.log("websocket closed", event)
  writer.close()
}

ws.onerror = (event) => {
  console.log("websocket error", event)
}

any hint on this? no error, just a empty file downloaded

[AlwaysNoobCoder]

sorry, I need new TextEncoder.encode(event.data)