Multiple transitions with scss

In your mixin, you have declared a single variable $x as a parameter which means that sass expects the mixin to be called with one argument.

@include transition(visibility 0s ease 0.2s)

When you pass the mixin comma separated values, it causes an error because sass sees these as multiple values instead of a single value which it expects.

@include transition(visibility 0s ease 0.2s, opacity 0.2s ease) //Sees two args instead of one arg

In Sass, comma separated values can be interpreted as a single value if declared as varargs. Varargs are mixin or function parameters declared with 3 dots appended to their name.

Replacing your $x parameter with $x... will ensure that sass interprets the comma separated arguments passed to your mixin as one value.

@mixin transition($x...){
  -webkit-transition: $x;
  -moz-transition: $x;
  -ms-transition: $x;
  -o-transition: $x;
  transition: $x;
}

It can then be used like this

div {
  @include transition(color 1s, background-color 1s, border-color 1s);
}

which compiles to

div {
  -webkit-transition: color 1s, background-color 1s, border-color 1s;
  -moz-transition: color 1s, background-color 1s, border-color 1s;
  -ms-transition: color 1s, background-color 1s, border-color 1s;
  -o-transition: color 1s, background-color 1s, border-color 1s;
  transition: color 1s, background-color 1s, border-color 1s;
}

By doing this you can pass the values as you normally would in CSS without the hack you are currently using making it much cleaner.

Hope this helps

Since this is the first result on Google, I want to say that this does not solve my problem. I wanted to transition multiple properties, with only one mixin. I came up with this solution: (see link for helper functions)

/*
  usage: @include transition(prop1, prop2, ..., 0.5s cubic-bezier(0.16, 0.85, 0.45, 1));
*/
@mixin transition($args...) {
  $type: nth($args, length($args));
  $props: remove-nth($args, length($args));
  $result: ();

  @for $i from 1 through length($props) {
    $prop: nth($props, $i);
    $result: append($result, $prop);
    $result: append($result, $type);
    @if $i != length($props) {
      $result: append($result, unquote($string: ","));
    }
  }

  @include simple_transition($result);
}

I created a short mixin that allows adding multiple transition properties in one declaration. In case number of arguments provided for the timing, easing or delay, is less than number of transition properties, the arguments are repeated.

@mixin transition($prop, $time, $easing: $ease1, $delay: 0s) {
    $transition: ();
    @for $i from 1 through length($prop) {
        @for $j from 0 to (length($prop)) - (length($time)) {
            $time: join($time, nth($time, -1));
        }
        @for $j from 0 to (length($prop)) - (length($easing)) {
            $easing: join($easing, nth($easing, -1));
        }
        @for $j from 0 to (length($prop)) - (length($delay)) {
            $delay: join($delay, nth($delay, -1));
        }

        $transition: append(
            $transition,
            (nth($prop, $i) nth($time, $i) nth($easing, $i) nth($delay, $i)),
            $separator: comma
        );
    }
    transition: $transition;
}

//scss input:
@include transition(height width transform, 0.2s 0.3s, linear, 0s);

//css output:
transition: height 0.2s linear 0s, width 0.3s linear 0s, transform 0.3s linear 0s;