_str-last-index.scss

@function str-last-index($string, $substr) {
  $index: null;
  $length: str-length($string);
  @for $n from $length through 1 {
    $index: str-index(str-slice($string, $n, $length), $substr);
    @if $index { @return $index + $n - 1; }
  }
  @return $index;
}