Clock in JavaScript

by bc_rikko

HTML

<section class="clock">
  <div class="dials">
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
  </div>
  <div class="hour hand"></div>
  <div class="minute hand"></div>
  <div class="second hand"></div>
</section>

CSS

.clock {
  position: relative;
  width: 300px;
  height: 300px;
  border-radius: 50%;
  border: solid 2px silver;
}

.clock::after {
  content: "";
  position: absolute;
  top: calc(50% - 8px);
  left: calc(50% - 8px);
  border-radius: 50%;
  width: 16px;
  height: 16px;
  background-color: silver;
}

.dials {
  position: relative;
  width: 100%;
  height: 100%;
}

.dials > div {
  position: absolute;
  top: 0;
  left: calc(50% - 3px);
  width: 6px;
  height: 50%;
  transform-origin: bottom;
}
.dials > div::after {
  position: absolute;
  top: 0;
  content: "";
  width: 6px;
  height: 15px;
  background-color: silver;
}

.dials div:nth-child(1) { transform: rotate(30deg); }
.dials div:nth-child(2) { transform: rotate(60deg); }
.dials div:nth-child(3) { transform: rotate(90deg); }
.dials div:nth-child(4) { transform: rotate(120deg); }
.dials div:nth-child(5) { transform: rotate(150deg); }
.dials div:nth-child(6) { transform: rotate(180deg); }
.dials div:nth-child(7) { transform: rotate(210deg); }
.dials div:nth-child(8) { transform: rotate(240deg); }
.dials div:nth-child(9) { transform: rotate(270deg); }
.dials div:nth-child(10) { transform: rotate(300deg); }
.dials div:nth-child(11) { transform: rotate(330deg); }
.dials div:nth-child(12) { transform: rotate(360deg); }

.hand {
  position: absolute;
  bottom: 50%;
  left: 50%;
  background-color: silver;
  transform-origin: 50% 100%;
}

.hour.hand {
  width: 6px;
  height: 90px;
}

.minute.hand {
  width: 4px;
  height: 140px;
}

.second.hand {
  width: 2px;
  height: 130px;
}

JavaScript

const hour = document.querySelector(".hour.hand");
const minute = document.querySelector(".minute.hand");
const second = document.querySelector(".second.hand");

setInterval(() => {
  const date = new Date();
  const s = (360 / 60) * date.getSeconds();
  const m = (360 / 60) * date.getMinutes() + (s / 60);
  const h = (360 / 24) * date.getHours() + (m / 24);
  
  second.style.transform = `rotate(${s}deg)`;
  minute.style.transform = `rotate(${m}deg)`;
  hour.style.transform = `rotate(${h}deg)`;
}, 1000);