clock

custom.js

'use strict'

const time = document.getElementById('time')

function updateTime() {
  const currentTime = new Date()
  const hh = currentTime.getHours()
  const mm = currentTime.getMinutes()
  const ss = currentTime.getSeconds()
  // Format time to iprefix 0 if < 10
  const formattedTime = `${zeroPadder(hh)} : ${zeroPadder(mm)} : ${zeroPadder(ss)}`

  time.innerHTML = formattedTime
}

function zeroPadder(n) {
	return (parseInt(n, 10) < 10 ? '0' : '') + n
}

updateTime()

setInterval(updateTime, 1000)

index.html

<!DOCTYPE html>
<html>

<head>
  <meta charset="utf-8">
  <title>JavaScript Clock</title>
  <meta name="robots" content="noindex, nofollow">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="stylesheet" href="styles.css">
</head>

<body>
  <header>
    <h1>JavaScript Clock</h1>
  </header>
  <div class="wrapper">
    <div class="container">
      <time id="time"></time>
    </div>
    <!-- .container-->
  </div>
  <!-- .wrapper-->
  <footer>
    <small><a href="https://opensource.org/licenses/MIT">MIT</a></small>
  </footer>
  <script src="custom.js">
  </script>
</body>

</html>

styles.css

body {
  background: #eeeeee;
  font-size: 16px;
  font-family: "Trebuchet MS", Helvetica, sans-serif;
  margin: 0;
}

a {
  color: crimson;
  text-decoration: none;
}

a:hover {
  color: red;
}


/* Layout
------------------------------------------*/

header,
.container,
footer {
  margin: 0 auto;
  width: 88%;
  max-width: 1080px;
}

.wrapper {
  padding: 1em 0;
  background: #ffffff;
}


/* Table
------------------------------------------*/

td:first-child {
  text-align: right;
}

td {
  padding: .5em 0 .5em .7em;
}

.calculator {
  max-width: 266px;
  display: flex;
  flex-direction: column;
  align-items: flex-end;
}

input {
  font-size: 1em;
  background: linear-gradient(#eeeeee, #ffffff);
  border-top: 2px solid #cccccc;
  border-left: 2px solid #cccccc;
  border-bottom: 2px solid #eeeeee;
  border-bottom: 2px solid #eeeeee;
  padding: .5em;
}

button {
  font-size: 1em;
  border: none;
  background: linear-gradient(#ffffff, #eeeeee);
  outline: 0;
  padding: .5em 1em;
  border-radius: 15px;
  text-shadow: 1px 1px 3px rgba(198, 198, 198, 0.9);
  border: 2px solid #eeeeee;
}

button:hover {
  background: linear-gradient(#eeeeee, #ffffff);
}