Using CSS Custom Properties to streamline animation

07 Dec 2019

Thanks to a great tip from Lucas Hugdahl on Twitter, here’s how to use CSS custom properties (variables) in your transforms so you don't need to rewrite the whole transform rule in order to transition (animate) a single property.

Let’s take the simple example of a button that we want to increase in size when hovered.

By using a custom property for the scale value, we can keep things DRYer in our :hover rule by only updating that variable rather than rewriting the entire transform rule.

The button HTML:

<button>Hover over me</button>

CSS:

button {
  transition: transform .5s ease-in-out;
  transform: translateX(-50%) translateY(-50%) scale(var(--scale, 1));
}

button:hover {
  --scale: 2;
}

See it in action on Codepen.