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javascript - Paho Javascript MQTT 订阅多个主题

问题描述

message_callback_add当客户端订阅多个主题时，是否可以使用与 paho python 中使用的类似概念（在 javascript 中）来使用多个回调？我已经看到了if条件的使用，onMessageArrived()但我想知道是否存在更有效和更清洁的方法？

var mqtt;                           // MQTT variable/object
var reconnectTimeout = 5000;        // 5 seconds for the reconnectTimeout
var host="localhost";               // MQTT bridge IP
var port=8083;                      // MQTT bridge port 
MQTTconnect();                      // Initialise the MQTT connections

function MQTTconnect(){
  console.log("mqtt connecting to " + host + ":" + port);
  mqtt = new Paho.MQTT.Client(host, port, "client_test");
  var options = {
    timeout: 100,
    onSuccess: onConnect,
    onFailure: onFailure,
  };
  mqtt.onMessageArrived = onMessageArrived;
  mqtt.connect(options); // connect
}

function onConnect(){
  console.log("Mqtt Connected - Subscribe to the topics");
  mqtt.subscribe("topic1/a");
  mqtt.subscribe("topic2/b");
}
            
function onFailure(message){
  console.log("Connection attempt to MQTT " + host + " failed");
  setTimeout(MQTTconnect, reconnectTimeout);
}

function onMessageArrived(msg){
  if (msg.destinationName == "topic1/a"){
    console.log("Topic1: ", msg.payloadString);
  }
  else if (msg.destinationName == "topic2/b"){
    console.log("Topic2: ", msg.payloadString);
  }
}

标签： javascriptmqttpaho

解决方案

不，JavaScript 中的所有消息只有一个回调。

onMessageArrived唯一的选择是在回调中根据需要检查主题和分支

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