More dynamic, oldIE-compatible SCSS function for rgba

rgbaa.scss

@function rgbaa($args...) {

  // rgbaa(#FFF, .5)
  @if length($args) == 2 {
    $hex: nth($args, 1);
    $alpha: nth($args, 2);
    @if $oldIE == 1 {
      @return rgb(red($hex), green($hex), blue($hex));
    } @else {
      @return rgba(red($hex), green($hex), blue($hex), $alpha);
    }

  // rgbaa(20, 30, 40, .5)
  } @else if length($args) == 4 {
    @if $oldIE == 1 {
      @return rgb(nth($args, 1), nth($args, 2), nth($args, 3));
    } @else {
      @return rgba(nth($args, 1), nth($args, 2), nth($args, 3), nth($args, 4));
    }
  }
}