postcss-custom-properties
Advanced tools
The postcss-custom-properties npm package is a PostCSS plugin that allows you to use CSS Custom Properties (also known as CSS variables) in environments that do not support them natively. It transforms CSS variables into static values based on your configurations, making it easier to maintain themes and styles dynamically across your project.
Transform CSS Custom Properties
This feature allows the transformation of CSS custom properties into their corresponding static values. It is useful for supporting older browsers that do not understand CSS variables.
/* Input CSS */
:root {
--main-color: red;
}
a {
color: var(--main-color);
}
/* Output CSS */
a {
color: red;
}Preserve option
With the preserve option set to true, the plugin outputs both the transformed static value and the original variable. This is useful for progressive enhancement.
/* Input CSS */
:root {
--main-color: red;
}
a {
color: var(--main-color);
}
/* Output CSS with preserve: true */
a {
color: red;
color: var(--main-color);
}cssnext is a PostCSS plugin that allows you to use future CSS features today. It includes support for CSS custom properties among other features. Compared to postcss-custom-properties, cssnext offers a broader range of CSS features but might be heavier due to its comprehensive nature.
postcss-preset-env lets you convert modern CSS into something most browsers can understand, determining the polyfills you need based on your targeted browsers or runtime environments. It includes handling of CSS custom properties as part of its feature set, similar to postcss-custom-properties, but is more configurable and includes various stages of CSS specifications.
PostCSS Custom Properties lets you use Custom Properties in CSS, following the CSS Custom Properties specification.
:root {
--color-blue-dark: rgb(0, 61, 184);
--color-blue-light: rgb(0, 217, 255);
--color-pink: rgb(255, 192, 211);
--text-color: var(--color-pink);
}
.element {
/* custom props */
--border-color: var(--color-blue-light);
/* props */
border: 1px solid var(--border-color);
color: var(--text-color);
}
.element--dark {
--border-color: var(--color-blue-dark);
}
/* becomes */
:root {
--color-blue-dark: rgb(0, 61, 184);
--color-blue-light: rgb(0, 217, 255);
--color-pink: rgb(255, 192, 211);
--text-color: var(--color-pink);
}
.element {
/* custom props */
--border-color: var(--color-blue-light);
/* props */
border: 1px solid rgb(0, 217, 255);
border: 1px solid var(--border-color);
color: rgb(255, 192, 211);
color: var(--text-color);
}
.element--dark {
--border-color: var(--color-blue-dark);
}
Note: This plugin only processes variables that are defined in the :root or html selector.
Locally defined custom properties will be used as fallbacks only within the same rule, but not elsewhere.
Add PostCSS Custom Properties to your project:
npm install postcss postcss-custom-properties --save-dev
Use it as a PostCSS plugin:
const postcss = require('postcss');
const postcssCustomProperties = require('postcss-custom-properties');
postcss([
postcssCustomProperties(/* pluginOptions */)
]).process(YOUR_CSS /*, processOptions */);
PostCSS Custom Properties runs in all Node environments, with special instructions for:
| Node | PostCSS CLI | Webpack | Create React App | Gulp | Grunt |
|---|
The preserve option determines whether properties using
custom properties should be preserved in their original form. By default these are preserved.
Custom property declarations are always preserved only var() functions can be omitted.
postcssCustomProperties({ preserve: false })
:root {
--color-blue-dark: rgb(0, 61, 184);
--color-blue-light: rgb(0, 217, 255);
--color-pink: rgb(255, 192, 211);
--text-color: var(--color-pink);
}
.element {
/* custom props */
--border-color: var(--color-blue-light);
/* props */
border: 1px solid var(--border-color);
color: var(--text-color);
}
.element--dark {
--border-color: var(--color-blue-dark);
}
/* becomes */
:root {
--color-blue-dark: rgb(0, 61, 184);
--color-blue-light: rgb(0, 217, 255);
--color-pink: rgb(255, 192, 211);
--text-color: var(--color-pink);
}
.element {
/* custom props */
--border-color: var(--color-blue-light);
/* props */
border: 1px solid var(--border-color);
color: rgb(255, 192, 211);
}
.element--dark {
--border-color: var(--color-blue-dark);
}
FAQs
Use Custom Properties Queries in CSS
The npm package postcss-custom-properties receives a total of 5,701,445 weekly downloads. As such, postcss-custom-properties popularity was classified as popular.
We found that postcss-custom-properties demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 5 open source maintainers collaborating on the project.
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