How to get the current time in Google spreadsheet using script editor?

use the JavaScript Date() object. There are a number of ways to get the time, date, timestamps, etc from the object. (Reference)

function myFunction() {
  var d = new Date();
  var timeStamp = d.getTime();  // Number of ms since Jan 1, 1970

  // OR:

  var currentTime = d.toLocaleTimeString(); // "12:35 PM", for instance
}