MQTT newbie troubles

Thank you, Gordon.
do you mean put it in order like this?

function mqttRun(){
  var server = 'my_broker';
  var options = {
          keep_alive: 60,
          port: my_port,
          clean_session: my_port,
          username: "my_user",
          password: "my_pass",
          protocol_name: "MQTT",
          protocol_level: 4,
  };
  var mqtt = require("MQTT").create(server);
    mqtt.on('connected', function() {
    mqtt.subscribe("test");
  });

  
  mqtt.connect(options);
}

I tried now - same error

>mqttRun()
Client connected
Uncaught Error: Function "write" not found!

What I'm doing wrong?
UPD. I saw this subject - http://forum.espruino.com/conversations/293870
example in post #5 and mine shoud do the same, but they don't