Responsive-modular-scale.css NPM

responsive-modular-scale.css

Responsive typography using CSS variables

This implements a basic Modular Scale system using CSS variables. Use this with postcss-cssnext and postcss-import.

Installation

# using Yarn
yarn add --exact responsive-modular-scale.css

# using npm
npm install --save --save-exact responsive-modular-scale.css

Usage

responsive-modular-scale.css can be used in 3 different ways:

Functional selectors (`postcss-extend-rule`)

See § Usage as functional selectors.

.title {
  @extend %ms-font-size-2;
}

Property sets (`postcss-apply`)

See § Usage as property sets.

.title {
  @apply --ms-font-size-2;
}

CSS modules

See § Usage as a CSS module.

.title {
  composes: msFontSize2 from 'responsive-modular-scale.css/modularscale.module.css';
}

How it works

To use it, use any of the provided --font-size-# custom property sets:

div {
  @apply --font-size-4;
}

This applies a font-size: 2.0736rem declaration for desktops—the default ratio is 1.2, so that's 1rem * 1.2 ^ 4. For mobiles and tablets, it will use a different ratio (1.15 and 1.17 by default).

div {
  font-size: 1.74901rem;
}

@media (min-width: 481px) {
  div {
    font-size: 1.87389rem;
  }
}

@media (min-width: 769px) {
  div {
    font-size: 2.0736rem;
  }
}

Configuring settings

Set up a variables.css with your configuration. Consider placing this wherever you put your common variables (eg, color palettes and font names). See: defaults.css.

:root {
  --ms-ratio-sm: 1.15;
  --ms-ratio-md: 1.17;
  --ms-ratio-lg: 1.2;
  --ms-base: 1rem;
  --ms-base-sm: var(--ms-base);
  --ms-base-md: var(--ms-base-sm);
  --ms-base-lg: var(--ms-base-md);
}

@custom-media --ms-viewport-md (width > 480px);
@custom-media --ms-viewport-lg (width > 768px);

Usage as functional selectors

To use this as functional selectors (ie, @extend), you'll need these PostCSS plugins:

Configure PostCSS to load these plugins and import your variables. Here's an example config:

/* postcss.config.js */
module.exports = ctx => {
  return {
    plugins: [
      // ...
      require('postcss-prepend-imports')({
        files: [
          require.resolve(
            'responsive-modular-scale.css/responsive-modular-scale.css'
          )
        ]
      }),
      require('postcss-extend-rule')(),
      require('postcss-preset-env')({
        importFrom: [require.resolve('./your/path/to/variables.css')]
      })
      // ...
    ]
  }
}

You'll then be able to use them with @extend in your CSS.

.title {
  @extend %ms-font-size-2;
}

These selectors will become available:

@extend %ms-font-size--1 (negative 1)
@extend %ms-font-size-0 (applies the base font size)
@extend %ms-font-size-1
@extend %ms-font-size-2
...
@extend %ms-font-size-20

Usage as property sets

You can also apply modular scale font sizes using CSS property sets (aka, @apply). You'll need these PostCSS plugins:

Configure PostCSS to load these plugins and import your variables. Here's an example config:

/* postcss.config.js */
module.exports = ctx => {
  return {
    plugins: [
      // ...
      require('postcss-prepend-imports')({
        files: [
          require.resolve(
            'responsive-modular-scale.css/responsive-modular-scale.css'
          )
        ]
      }),
      require('postcss-extend-rule')(),
      require('postcss-preset-env')({
        importFrom: [require.resolve('./your/path/to/variables.css')]
      })
      // ...
    ]
  }
}

You'll then be able to use them with @apply in your CSS.

.title {
  @apply --ms-font-size-2;
}

These property sets will become available:

@apply --font-size--1 (negative 1)
@apply --font-size-0 (applies the base font size)
@apply --font-size-1
@apply --font-size-2
...
@apply --font-size-20

Usage as a CSS module

:warning: Experimental - You can apply modular scale font sizes using CSS modules.

To use this as functional selectors (ie, @extend), you'll need these PostCSS plugins:

postcss-preset-env

Configure PostCSS to load these plugins and import your variables. Here's an example config:

/* postcss.config.js */
module.exports = ctx => {
  return {
    plugins: [
      // ...
      require('postcss-preset-env')({
        importFrom: [require.resolve('./your/path/to/variables.css')]
      })
      // ...
    ]
  }
}

You'll then be able to use them with composes in your CSS.

.myButton {
  composes: msFontSize2 from 'responsive-modular-scale.css/modularscale.module.css';
}

These CSS classes are available:

msFontSizeMinus1 (negative 1)
msFontSize0 (applies the base font size)
msFontSize1
msFontSize2
...
msFontSize20

Learn more about the composes: property from the CSS modules documentation.

Prior art

postcss-modular-scale is a PostCSS plugin. However, it doesn't support responsive ratios, and the syntax is non-standard CSS.
modularscale-sass is, in my opinion, the gold standard modular scale implementation. It only supports Sass, however.