Speedy CSS Tip! Animated Loader

Let's make an animated CSS loader with scoped custom properties and animation-timing-function

Jhey Tompkins

Hop over to CodePen and create a new pen.

Create the markup for our loader. Note the use of inline custom properties:

<div class="loader" style="--count: 10">
  <span style="--index: 0"></span>
  <span style="--index: 1"></span>
  <span style="--index: 2"></span>
  <span style="--index: 3"></span>
  <span style="--index: 4"></span>
  <span style="--index: 5"></span>
  <span style="--index: 6"></span>
  <span style="--index: 7"></span>
  <span style="--index: 8"></span>
  <span style="--index: 9"></span>
</div>

You can also use a generator (Pug) to configure the number of lines:

- const COUNT = 10
.loader(style=`--count: ${COUNT}`)
  - let i = 0
  while i < COUNT
    span(style=`--index: ${i}`)
    - i++

Give our loader some styles:

loader {
  --size: 10vmin;

  height: var(--size);
  position: relative;
  width: var(--size);
}

Position our lines using absolute positioning and a combination of calc with transform:

.loader span {
  background: grey;
  height: 25%;
  left: 50%;
  position: absolute;
  top: 50%;
  transform: translate(-50%, -50%)
             rotate(calc(((360 / var(--count)) * var(--index)) * 1deg))
             translate(0, -125%);
  width: 10%;
}

Apply an opacity based on the --index:

.loader span {
  opacity: calc(var(--index) / var(--count));
} 

Get things spinning!

.loader {
  animation: spin 0.75s infinite steps(var(--count));
}

@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}

Note the use of steps(var(--count)) to get the right effect ✨

Done! 🎉

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Stay Awesome! ʕ •ᴥ•ʔ