How to return value after serial communication NodeJS

Question

I'm new in JS and async... so I need help :) I need to return value after serial communication. reading serial apparently need to be function, so I dont know how to make it blocking, or return value from it... console log shows value, but value is not returned...(probably because its executed before serial). please help. Here is part of code:

var LightController = {
 getBrightness: function() { //get brightness
    port.write(askcommand);
    port.on('data', function (data) {
       st = data.slice(-4, -3);
       this.brightness = st.readInt8(0);
       console.log(this.brightness)
    });
    return this.brightness;
  },    

lightAccessory
      .getService(Service.Lightbulb)
      .addCharacteristic(Characteristic.Brightness)
      .on('get', function(callback) {
        callback(null, LightController.getBrightness());
      });

score 0 · Accepted Answer · answered Mar 26 '17 at 12:02

var LightController = {
 // add callback to get brightness function
 getBrightness: function(brightnessCallback) { //get brightness
    port.write(askcommand);
    port.on('data', function (data) {
       st = data.slice(-4, -3);
       this.brightness = st.readInt8(0);
       console.log(this.brightness)
       // call callback for get brightness function
       brightnessCallback(this.brightness);
    });
    return this.brightness;
  }
}

lightAccessory
      .getService(Service.Lightbulb)
      .addCharacteristic(Characteristic.Brightness)
      .on('get', function(callback) {
          // call the get brightness function, passing anonymous function as brightness callback
          LightController.getBrightness(function(brightness){
            // call original callback with brightness
            callback(null, brightness);
          })
      });

How to return value after serial communication NodeJS

1 Answers1