function timeLeftTodayAsClock() {
  //let totalMillisecondsInADay = (new Date('Jan 01 1970 23:59:59:999 GMT+0000')).getTime() + 1; // the one just flips the 999 to 0000
  const totalMillisecondsInADay = 86400000; // number of ms in a day
  return  (new Date(totalMillisecondsInADay - Date.now())).toString().match(/\d\d:\d\d:\d\d/)[0];
}

console.log(timeLeftTodayAsClock());

//output looks like 12:23:38
//NB: Works for one day, e.g on a deal/auction website