JS Bin // source https://jsbin.com/mecumom

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  <meta charset="utf-8">
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  <title>JS Bin</title>
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var compose = function compose() {
  for (var _len = arguments.length, fns = Array(_len), _key = 0; _key < _len; _key++) {
    fns[_key] = arguments[_key];
  }

return function (arg) {
    return fns.reduce(function (composed, f) {
      return f(composed);
    }, arg);
  };
};

var oneSecond = function oneSecond() {
  return 1000;
};

var getCurrentTime = function getCurrentTime() {
  return new Date();
};

var clear = function clear() {
  return console.clear();
};

var log = function log(message) {
  return console.log(message);
};

var serializeClockTime = function serializeClockTime(date) {
  return {
    hours: date.getHours(),
    minutes: date.getMinutes(),
    seconds: date.getSeconds()
  };
};

var civilianHours = function civilianHours(clockTime) {
  return _extends({}, clockTime, {
    hours: clockTime.hours > 12 ? clockTime.hours - 12 : clockTime.hours
  });
};

var appendAMPM = function appendAMPM(clockTime) {
  return _extends({}, clockTime, {
    ampm: clockTime.hours >= 12 ? 'PM' : 'AM'
  });
};

var display = function display(target) {
  return function (time) {
    return target(time);
  };
};

var formatClock = function formatClock(format) {
  return function (time) {
    return format.replace('hh', time.hours).replace('mm', time.minutes).replace('ss', time.seconds).replace('tt', time.ampm);
  };
};

var convertToCivilianTime = function convertToCivilianTime(clockTime) {
  return compose(appendAMPM, civilianHours)(clockTime);
};

var doubleDigits = function doubleDigits(civilianTime) {
  return compose(prependZero('hours'), prependZero('minutes'), prependZero('seconds'))(civilianTime);
};

var startTicking = function startTicking() {
  return setInterval(compose(clear, getCurrentTime, serializeClockTime, convertToCivilianTime, doubleDigits, formatClock('hh:mm:ss tt'), display(log)), oneSecond());
};
startTicking();

log(civilianHours(serializeClockTime(getCurrentTime())));
</script>

const oneSecond = () => 1000;

const getCurrentTime = () => new Date();

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

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

const serializeClockTime = date => 
  ({
    hours: date.getHours(),
    minutes: date.getMinutes(),
    seconds: date.getSeconds()
  });

const civilianHours = clockTime => 
  ({
    ...clockTime,
    hours: (clockTime.hours > 12) ? 
      clockTime.hours - 12 : 
      clockTime.hours
  });

const appendAMPM = clockTime => 
  ({
    ...clockTime,
    ampm: (clockTime.hours >= 12) ? 'PM' : 'AM'
  });

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

const formatClock = format => 
    time => 
      format.replace('hh', time.hours)
            .replace('mm', time.minutes)
            .replace('ss', time.seconds)
            .replace('tt', time.ampm);

const prependZero = key => clockTime => 
  ({
    ...clockTime,
    [key]: (clockTime[key] < 10) ? 
      '0' + clockTime[key] : 
      clockTime[key]
  });

const convertToCivilianTime = clockTime => 
  compose(
    appendAMPM,
    civilianHours
  )(clockTime);

const doubleDigits = civilianTime => 
  compose(
    prependZero('hours'),
    prependZero('minutes'),
    prependZero('seconds'),
  )(civilianTime);

const startTicking = () => 
  setInterval(
    compose(
      clear,
      getCurrentTime,
      serializeClockTime,
      convertToCivilianTime,
      doubleDigits,
      formatClock('hh:mm:ss tt'),
      display(log)
    ), 
    oneSecond()
  )
startTicking();

log(civilianHours(serializeClockTime(getCurrentTime())))</script></body>
</html>