GPS modul. How to get speed and put it in variable?

Wow great. it works!!!

Serial3.setup (115200, {rx: P0, tx: P1});
var lastData;
var gps = require ("GPS"). connect (Serial3, function (data) {
  
  if (lastData) {
   // do stuff here - eg. the difference between the two readings
    var dlat =data.time;
 //   var dlon = data.lon - lastData.lon;   
  console.log (dlat);
 console.log ('*->',lastData);
 
  }
  

  lastData = data.time;
 // return lastData;
});