Вадим

--output[=FIELD_LIST]
              use the output format defined by FIELD_LIST, or print all fields if FIELD_LIST is omitted.

И далее внизу:

       FIELD_LIST is a comma-separated list of columns to be included.  Valid field names are: 'source', 'fstype', 'itotal', 'iused', 'iavail', 'ipcent', 'size',
       'used', 'avail', 'pcent', 'file' and 'target' (see info page).

const WebSocket = require('ws');

const ws = new WebSocket('wss://dallas.tx.publicsearch.us/ws', {
  headers: {
    "Origin": "https://dallas.tx.publicsearch.us",
    "Cookie": "authToken=51f69ac5-67c5-41ac-8943-cace7ebc6b3c; authToken.sig=x9S_G8Lwy6KHaB2Ek4PT1PR7jhE;"
  }
});

ws.on('open', () => {
  console.log('Соединение открыто');
});

ws.on('close', (code, reason) => {
  console.log('Соединение закрыто', code, reason);
});

--stdout
    Write all messages to stdout.