[Fixed] how to execute a function only once every X milliseconds?

Issue

im pretty new into javascript and node, currently working into a node.js app,
the app use express and mongoDB, the idea is listen to some third party services via webhook, websocket and mqtt and store all data into mongoDB.

but I have a litle problem, some of the third party apps send me data too often,
for example, the mqtt stream sends about 2 message every second, i need to store only one of those message every minute.

this is the way I instance mqtt into app.js

var mqttHandler = require('./mqtt/mqtt_handler'); //mqtt
var mqttClient = new mqttHandler(); //mqtt
mqttClient.connect(); //mqtt

this is my mqttHandler.js:

onst mqtt = require('mqtt');

class MqttHandler {
  constructor() {
    this.mqttClient = null;
    this.host = 'mqtts://host';
    this.username = 'foo'; // mqtt credentials if these are needed to connect
    this.password = 'mypassqword';
    this.port = 8083;
    this.protocol = 'MQTTS';
    this.client = 'bar'
  }

  connect() {
    // Connect mqtt with credentials (in case of needed, otherwise we can omit 2nd param)
    this.mqttClient = mqtt.connect(this.host, {password : this.password, username : this.username, port: this.port});

    // Mqtt error calback
    this.mqttClient.on('error', (err) => {
      console.log(err);
      this.mqttClient.end();
    });

    // Connection callback
    this.mqttClient.on('connect', () => {
      //console.log(`mqtt client connected`);
    });

    // mqtt subscriptions
    this.mqttClient.subscribe('/the_subscription');
    // When a message arrives, console.log it
    this.mqttClient.on('message', function (topic, message) {
      console.log(message.toString())
    });

    this.mqttClient.on('close', () => {
      //console.log(`mqtt client disconnected`);
    });
  }

  // Sends a mqtt message to topic: mytopic
  sendMessage(message) {
    this.mqttClient.publish('mytopic', message);
  }
}

module.exports = MqttHandler;

i’veing reading about setInterval and setTimeout, but I can’t figure out how to implement these to force a given function to only run once every X seconds (no mather how many times it is called)

could there be a similar / generic way to implement this feature for both, mqtt, webohooks and / or websocket?

I took this example about how to implement mqtt from a tutorial, its working perfect, as I said, im prettty new to javascript.

Solution

One naive approach using setInterval is to set a flag regularly and clear it once a message is posted. The ignore any other messages until the flag is set again by the interval function.

let readyToPost = false;
setInterval(function(){ readyToPost = true; }, 1000);

In your function:

function connect() {
  if (!readyToPost) return;  // do nothing
  readyToPost = false;
  // rest of your code
}