Responsive Web Design creations often exist over several different breakpoints. Managing those breakpoints is not always easy. Using them and updating them can sometimes be tedious. Hence the need for a mixin to handle breakpoint configuration and usage.

#Simple version

First you need a map of breakpoints, associated to names.

$breakpoints: (
  'small':  767px,
  'medium': 992px,
  'large':  1200px
) !default;

Then, the mixin will use this map.

/// Mixin to manage responsive breakpoints
/// @author Hugo Giraudel
/// @param {String} $breakpoint - Breakpoint name
/// @require $breakpoints
@mixin respond-to($breakpoint) {
  // If the key exists in the map
  @if map-has-key($breakpoints, $breakpoint) {
    // Prints a media query based on the value
    @media (min-width: map-get($breakpoints, $breakpoint)) {
      @content;
    }
  }
 
  // If the key doesn't exist in the map
  @else {
    @warn "Unfortunately, no value could be retrieved from `#{$breakpoint}`. "
        + "Available breakpoints are: #{map-keys($breakpoints)}.";
  }
}

Usage:

.selector {
  color: red;
  
  @include respond-to('small') {
    color: blue;
  }
}

Result:

.selector {
  color: red;
}
@media (min-width: 767px) {
  .selector {
    color: blue;
  }
}

#Advanced version

The simple version only makes it possible to use min-width media queries. To use more advanced queries, we can tweak our initial map and mixin a bit.

$breakpoints: (
  'small':  ( min-width:  767px ),
  'medium': ( min-width:  992px ),
  'large':  ( min-width: 1200px )
) !default;

/// Mixin to manage responsive breakpoints
/// @author Hugo Giraudel
/// @param {String} $breakpoint - Breakpoint name
/// @require $breakpoints
@mixin respond-to($breakpoint) {
  // If the key exists in the map
  @if map-has-key($breakpoints, $breakpoint) {
    // Prints a media query based on the value
    @media #{inspect(map-get($breakpoints, $breakpoint))} {
      @content;
    }
  }
 
  // If the key doesn't exist in the map
  @else {
    @warn "Unfortunately, no value could be retrieved from `#{$breakpoint}`. "
        + "Available breakpoints are: #{map-keys($breakpoints)}.";
  }
}

Usage:

.selector {
  color: red;
  
  @include respond-to('small') {
    color: blue;
  }
}

Result:

.selector {
  color: red;
}
@media (min-width: 767px) {
  .selector {
    color: blue;
  }
}