$placeholders: '-webkit-input-placeholder',
'-moz-placeholder',
'-ms-input-placeholder';

@mixin placeholder {
    @each $placeholder in $placeholders {
        @if $placeholder == "-webkit-input-placeholder" {
            &::#{$placeholder} {
                @content;
            }
        } @else if $placeholder == "-moz-placeholder" {
            // FF 18-
            &:#{$placeholder} {
                @content;
            }

            // FF 19+
            &::#{$placeholder} {
                @content;
            }
        } @else {
            &:#{$placeholder} {
                @content;
            }
        }
    }
}
