Mobile-first breakpoints and mediaqueries mixins

_mediaqueries.scss

// Functions
@function breakpoint-next($name, $breakpoints: $grid-breakpoints, $breakpoint-names: map-keys($breakpoints)) {
  $n: index($breakpoint-names, $name);
  @return if($n < length($breakpoint-names), nth($breakpoint-names, $n + 1), null);
}

@function breakpoint-min($name, $breakpoints: $grid-breakpoints) {
  $min: map-get($breakpoints, $name);
  @return if($min !=0, $min, null);
}

@function breakpoint-max($name, $breakpoints: $grid-breakpoints) {
  $next: breakpoint-next($name, $breakpoints);
  @return if($next, breakpoint-min($next, $breakpoints) - 1px, null);
}

// Mixins
@mixin media($name, $breakpoints: $grid-breakpoints) {
  $min: breakpoint-min($name, $breakpoints);
  @if $min {
    @media (min-width: $min) {
      @content;
    }
  } @else {
    @content;
  }
}

@mixin media-down($name, $breakpoints: $grid-breakpoints) {
  $max: breakpoint-max($name, $breakpoints);
  @if $max {
    @media (max-width: $max) {
      @content;
    }
  } @else {
    @content;
  }
}

// Breakpoints Map
$grid-breakpoints: (
  xs: 0,
  sm: 544px,
  md: 768px,
  lg: 992px,
  xl: 1200px
) !default;