Bootstrap4 grid system all mixins in a single file to use with bootstrap 3 or any scss based system

bootstrap4-grid-mixin-only.scss

@at-root {
  @-ms-viewport { width: device-width; } // stylelint-disable-line at-rule-no-vendor-prefix
}

html {
  box-sizing: border-box;
  -ms-overflow-style: scrollbar;
}

*,
*::before,
*::after {
  box-sizing: inherit;
}


// Bootstrap functions
//
// Utility mixins and functions for evalutating source code across our variables, maps, and mixins.

// Ascending
// Used to evaluate Sass maps like our grid breakpoints.
@mixin _assert-ascending($map, $map-name) {
  $prev-key: null;
  $prev-num: null;
  @each $key, $num in $map {
    @if $prev-num == null {
      // Do nothing
    } @else if not comparable($prev-num, $num) {
      @warn "Potentially invalid value for #{$map-name}: This map must be in ascending order, but key '#{$key}' has value #{$num} whose unit makes it incomparable to #{$prev-num}, the value of the previous key '#{$prev-key}' !";
    } @else if $prev-num >= $num {
      @warn "Invalid value for #{$map-name}: This map must be in ascending order, but key '#{$key}' has value #{$num} which isn't greater than #{$prev-num}, the value of the previous key '#{$prev-key}' !";
    }
    $prev-key: $key;
    $prev-num: $num;
  }
}

// Starts at zero
// Another grid mixin that ensures the min-width of the lowest breakpoint starts at 0.
@mixin _assert-starts-at-zero($map) {
  $values: map-values($map);
  $first-value: nth($values, 1);
  @if $first-value != 0 {
    @warn "First breakpoint in `$grid-breakpoints` must start at 0, but starts at #{$first-value}.";
  }
}

// Variables

$enable-grid-classes:       false !default;

// Grid breakpoints
//
// Define the minimum dimensions at which your layout will change,
// adapting to different screen sizes, for use in media queries.

$grid-breakpoints: (
  xs: 0,
  sm: 576px,
  md: 768px,
  lg: 992px,
  xl: 1200px
) !default;

@include _assert-ascending($grid-breakpoints, "$grid-breakpoints");
@include _assert-starts-at-zero($grid-breakpoints);


// Grid containers
//
// Define the maximum width of `.container` for different screen sizes.

$container-max-widths: (
  sm: 540px,
  md: 720px,
  lg: 960px,
  xl: 1140px
) !default;

@include _assert-ascending($container-max-widths, "$container-max-widths");


// Grid columns
//
// Set the number of columns and specify the width of the gutters.

$grid-columns:                12 !default;
$grid-gutter-width:           30px !default;


// Breakpoint viewport sizes and media queries.
//
// Breakpoints are defined as a map of (name: minimum width), order from small to large:
//
//    (xs: 0, sm: 576px, md: 768px, lg: 992px, xl: 1200px)
//
// The map defined in the `$grid-breakpoints` global variable is used as the `$breakpoints` argument by default.

// Name of the next breakpoint, or null for the last breakpoint.
//
//    >> breakpoint-next(sm)
//    md
//    >> breakpoint-next(sm, (xs: 0, sm: 576px, md: 768px, lg: 992px, xl: 1200px))
//    md
//    >> breakpoint-next(sm, $breakpoint-names: (xs sm md lg xl))
//    md
@function breakpoint-next($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);
}

// Minimum breakpoint width. Null for the smallest (first) breakpoint.
//
//    >> breakpoint-min(sm, (xs: 0, sm: 576px, md: 768px, lg: 992px, xl: 1200px))
//    576px
@function breakpoint-min($name, $breakpoints: $grid-breakpoints) {
  $min: map-get($breakpoints, $name);
  @return if($min != 0, $min, null);
}

// Maximum breakpoint width. Null for the largest (last) breakpoint.
// The maximum value is calculated as the minimum of the next one less 0.02px
// to work around the limitations of `min-` and `max-` prefixes and viewports with fractional widths.
// See https://www.w3.org/TR/mediaqueries-4/#mq-min-max
// Uses 0.02px rather than 0.01px to work around a current rounding bug in Safari.
// See https://bugs.webkit.org/show_bug.cgi?id=178261
//
//    >> breakpoint-max(sm, (xs: 0, sm: 576px, md: 768px, lg: 992px, xl: 1200px))
//    767.98px
@function breakpoint-max($name, $breakpoints: $grid-breakpoints) {
  $next: breakpoint-next($name, $breakpoints);
  @return if($next, breakpoint-min($next, $breakpoints) - .02px, null);
}

// Returns a blank string if smallest breakpoint, otherwise returns the name with a dash infront.
// Useful for making responsive utilities.
//
//    >> breakpoint-infix(xs, (xs: 0, sm: 576px, md: 768px, lg: 992px, xl: 1200px))
//    ""  (Returns a blank string)
//    >> breakpoint-infix(sm, (xs: 0, sm: 576px, md: 768px, lg: 992px, xl: 1200px))
//    "-sm"
@function breakpoint-infix($name, $breakpoints: $grid-breakpoints) {
  @return if(breakpoint-min($name, $breakpoints) == null, "", "-#{$name}");
}

// Media of at least the minimum breakpoint width. No query for the smallest breakpoint.
// Makes the @content apply to the given breakpoint and wider.
@mixin media-breakpoint-up($name, $breakpoints: $grid-breakpoints) {
  $min: breakpoint-min($name, $breakpoints);
  @if $min {
    @media (min-width: $min) {
      @content;
    }
  } @else {
    @content;
  }
}

// Media of at most the maximum breakpoint width. No query for the largest breakpoint.
// Makes the @content apply to the given breakpoint and narrower.
@mixin media-breakpoint-down($name, $breakpoints: $grid-breakpoints) {
  $max: breakpoint-max($name, $breakpoints);
  @if $max {
    @media (max-width: $max) {
      @content;
    }
  } @else {
    @content;
  }
}

// Media that spans multiple breakpoint widths.
// Makes the @content apply between the min and max breakpoints
@mixin media-breakpoint-between($lower, $upper, $breakpoints: $grid-breakpoints) {
  $min: breakpoint-min($lower, $breakpoints);
  $max: breakpoint-max($upper, $breakpoints);

  @if $min != null and $max != null {
    @media (min-width: $min) and (max-width: $max) {
      @content;
    }
  } @else if $max == null {
    @include media-breakpoint-up($lower, $breakpoints) {
      @content;
    }
  } @else if $min == null {
    @include media-breakpoint-down($upper, $breakpoints) {
      @content;
    }
  }
}

// Media between the breakpoint's minimum and maximum widths.
// No minimum for the smallest breakpoint, and no maximum for the largest one.
// Makes the @content apply only to the given breakpoint, not viewports any wider or narrower.
@mixin media-breakpoint-only($name, $breakpoints: $grid-breakpoints) {
  $min: breakpoint-min($name, $breakpoints);
  $max: breakpoint-max($name, $breakpoints);

  @if $min != null and $max != null {
    @media (min-width: $min) and (max-width: $max) {
      @content;
    }
  } @else if $max == null {
    @include media-breakpoint-up($name, $breakpoints) {
      @content;
    }
  } @else if $min == null {
    @include media-breakpoint-down($name, $breakpoints) {
      @content;
    }
  }
}


// Framework grid generation
//
// Used only by Bootstrap to generate the correct number of grid classes given
// any value of `$grid-columns`.

@mixin make-grid-columns($columns: $grid-columns, $gutter: $grid-gutter-width, $breakpoints: $grid-breakpoints) {
  // Common properties for all breakpoints
  %grid-column {
    position: relative;
    width: 100%;
    min-height: 1px; // Prevent columns from collapsing when empty
    padding-right: ($gutter / 2);
    padding-left: ($gutter / 2);
  }

  @each $breakpoint in map-keys($breakpoints) {
    $infix: breakpoint-infix($breakpoint, $breakpoints);

    // Allow columns to stretch full width below their breakpoints
    @for $i from 1 through $columns {
      .col#{$infix}-#{$i} {
        @extend %grid-column;
      }
    }
    .col#{$infix},
    .col#{$infix}-auto {
      @extend %grid-column;
    }

    @include media-breakpoint-up($breakpoint, $breakpoints) {
      // Provide basic `.col-{bp}` classes for equal-width flexbox columns
      .col#{$infix} {
        flex-basis: 0;
        flex-grow: 1;
        max-width: 100%;
      }
      .col#{$infix}-auto {
        flex: 0 0 auto;
        width: auto;
        max-width: none; // Reset earlier grid tiers
      }

      @for $i from 1 through $columns {
        .col#{$infix}-#{$i} {
          @include make-col($i, $columns);
        }
      }

      .order#{$infix}-first { order: -1; }

      .order#{$infix}-last { order: $columns + 1; }

      @for $i from 0 through $columns {
        .order#{$infix}-#{$i} { order: $i; }
      }

      // `$columns - 1` because offsetting by the width of an entire row isn't possible
      @for $i from 0 through ($columns - 1) {
        @if not ($infix == "" and $i == 0) { // Avoid emitting useless .offset-0
          .offset#{$infix}-#{$i} {
            @include make-col-offset($i, $columns);
          }
        }
      }
    }
  }
}


/// Grid system
//
// Generate semantic grid columns with these mixins.

@mixin make-container() {
  width: 100%;
  padding-right: ($grid-gutter-width / 2);
  padding-left: ($grid-gutter-width / 2);
  margin-right: auto;
  margin-left: auto;
}


// For each breakpoint, define the maximum width of the container in a media query
@mixin make-container-max-widths($max-widths: $container-max-widths, $breakpoints: $grid-breakpoints) {
  @each $breakpoint, $container-max-width in $max-widths {
    @include media-breakpoint-up($breakpoint, $breakpoints) {
      max-width: $container-max-width;
    }
  }
}

@mixin make-row() {
  display: flex;
  flex-wrap: wrap;
  margin-right: ($grid-gutter-width / -2);
  margin-left: ($grid-gutter-width / -2);
}

@mixin make-col-ready() {
  position: relative;
  // Prevent columns from becoming too narrow when at smaller grid tiers by
  // always setting `width: 100%;`. This works because we use `flex` values
  // later on to override this initial width.
  width: 100%;
  min-height: 1px; // Prevent collapsing
  padding-right: ($grid-gutter-width / 2);
  padding-left: ($grid-gutter-width / 2);
}

@mixin make-col($size, $columns: $grid-columns) {
  flex: 0 0 percentage($size / $columns);
  // Add a `max-width` to ensure content within each column does not blow out
  // the width of the column. Applies to IE10+ and Firefox. Chrome and Safari
  // do not appear to require this.
  max-width: percentage($size / $columns);
}

@mixin make-col-offset($size, $columns: $grid-columns) {
  $num: $size / $columns;
  margin-left: if($num == 0, 0, percentage($num));
}


// Container widths
//
// Set the container width, and override it for fixed navbars in media queries.

@if $enable-grid-classes {
  .container {
    @include make-container();
    @include make-container-max-widths();
  }
}

// Fluid container
//
// Utilizes the mixin meant for fixed width containers, but with 100% width for
// fluid, full width layouts.

@if $enable-grid-classes {
  .container-fluid {
    @include make-container();
  }
}

// Row
// Rows contain and clear the floats of your columns.

@if $enable-grid-classes {
  .row {
    @include make-row();
  }
  // Remove the negative margin from default .row, then the horizontal padding
  // from all immediate children columns (to prevent runaway style inheritance).
  .no-gutters {
    margin-right: 0;
    margin-left: 0;
    > .col,
    > [class*="col-"] {
      padding-right: 0;
      padding-left: 0;
    }
  }
}

// Columns
//
// Common styles for small and large grid columns

@if $enable-grid-classes {
  @include make-grid-columns();
}