Way back when I moved my site from plain HTML and CSS to Jekyll, I wanted to take full advantage of Sass and its powerful support for mixins. And one particularly repetitive line of code in my CSS went something like this:

.someSelector {
    transition: someProperty 0.2s ease,
                someOtherProperty 0.2s ease;
}

Why would I do this? Because I enjoy creating interactive experiences on my site that don't feel snappy—I love fluid transitions. But this gets repetitive after a while. And if there's one thing that developers hate, it's repetition.

A quick and dirty fix is to just create a Sass variable or CSS custom property that consolidates the shared parts of the transition:

$transition: 0.2s ease;

.someSelector {
    transition: someProperty $transition,
                someOtherProperty $transition;
}

But that still doesn't fully eliminate the repetition—we just have to type fewer characters now. What I was searching for is a Sass mixin for multiple CSS transitions. And I eventually found it in a StackOverflow answer by user yspreen:

mixins.scss 
@mixin transition($props...) {
    $result: ();

    @for $i from 1 through length($props) {
      $prop: nth($props, $i);
      $result: append($result, $prop);
      $result: append($result, ease 0.2s);

      @if $i != length($props) {
        $result: append($result, unquote($string: ","));
      }
    }

    transition: $result;
}

Of course, you can replace ease 0.2s with whatever standard transition you want all elements on your site to have.

Here's how this mixin works:

  1. It takes in a variable number of arguments.
  2. It loops over the arguments and accumulates a string taking the form property 0.2s ease,.
  3. It excludes the trailing comma for the very last property in the list.
  4. It sets the transition CSS property to be the result!

And here's how I use this multiple transition mixin in my own stylesheets:

.someProperty {
    @include transition(background-color, color, border-color);
}

It works like a charm, and it's super easy to understand!

Note that Tobias Ahlin created a more advanced version of the mixin that's able to cleanly handle overrides for things like the transition duration. Check it out if you need something more flexible!