nodemcu, esp8266, ds18s20

1. Should getTemp return the last value, even with a callback, rather than undefined?

2. here is how to avoid the intial bogus value:

   var sensors = s.map(function (device) {
   var t=ds.connect(ow, device);
   t.getTemp();
   return t;
   });
   
   sensors.forEach(function (sensor, index) {
     console.log('initial' + ": " + sensor.getTemp());
   });
   

This could be done automagically in the constructor here:

  this.type=parseInt(this.sCode[0]+this.sCode[1]);
  this.getTemp(); // trigger a conversion
}