SOURCE

// get one second
const oneSecond = () => 1000;

// clear console
const clear = () => console.clear();

// print message
const log = message => console.log(message);

// get current system time
const getCurrentTime = () => new Date();

// serialize time
const serializeClockTime = clockTime => ({
  year: clockTime.getFullYear(),
  month: clockTime.getMonth() + 1,
  day: clockTime.getDate(),
  hours: clockTime.getHours(),
  minutes: clockTime.getMinutes(),
  seconds: clockTime.getSeconds()
});

// append AM/PM to time
const appendAMPM = clockTime => ({...clockTime,
  ampm: clockTime.hours > 11 ? 'PM': 'AM'
});

// civilian hour
const civilianHour = clockTime => ({...clockTime,
  hours: clockTime.hours > 12 ? clockTime.hours - 12 : clockTime.hours
});

// format time
const formatClockTime = (formatter = 'yyyy-MM-dd hh:mm:ss') => ({
  year,
  month,
  day,
  hours,
  minutes,
  seconds,
  ampm
}) => formatter.replace('yyyy', year)
  .replace('MM', month)
  .replace('dd', day)
  .replace('hh', hours)
  .replace('mm', minutes)
  .replace('ss', seconds)
  .concat(' ').concat(ampm);

// prepend zero when number less then 10
const prependZero = clockTime => Object.keys(clockTime).reduce((previousClockTime, key) => ({...previousClockTime,
  [key] : clockTime[key] < 10 ? '0' + clockTime[key] : clockTime[key]
}), {});

// pipe
const compose = (...fns) => arg => fns.reduce((composed, f) => f(composed), arg);

// display message
const display = target => time => target(time);

// ticking method
const startTicking = () => setInterval(compose(clear, getCurrentTime, serializeClockTime, appendAMPM, civilianHour, prependZero, formatClockTime(), display(log)), oneSecond());

// start ticking
startTicking();