Live Demo: day and time in JavaScript

<!DOCTYPE html>
<html>

<body>
  <script>
    function dayTime() {
      const date = new Date();

      // it will return days name in number from 0 to 6
      var dayweek = date.getDay();

      // days name in word.
      var dayword = ['Sunday', 'Monday', 'Tuesday',
        'Wednesday', 'Thursday', 'Friday', 'Saturday'];

      // get current day of week
      var day = dayword[dayweek];

      // get hour, minute, and second
      var [hour, minutes, seconds] = [date.getHours(), date.getMinutes(),
      date.getSeconds()];

      // check whether am or pm
      var ampm = hour >= 12 ? 'PM' : 'AM';

      // convert hours in 12 clock format
      hour = hour % 12;

      var time = day + ' ' + hour + ":" + minutes + ":" + seconds + " " + ampm;
      document.getElementById("dayTimeValue").innerHTML = time;
    }
  </script>

  <h1>Day and time in javascript</h1>
  <h2>format in 'day of week' hour : minute : second</h2>
  <form>
    <input type="button" value="day and time" onclick="dayTime()">
    <p id="dayTimeValue">system date time</p>
  </form>
</body>

</html>