PostCSS Stepped Value Functions

npm install @csstools/postcss-stepped-value-functions --save-dev

PostCSS Stepped Value Functions lets you use round, rem and mod stepped value functions, following the CSS Values 4 specification.

.test-functions {
    padding: 8px mod(18px, 5px) 1px calc(rem(15px, 6px) + 50%);
    transform: rotate(mod(-140deg, -90deg));
    top: round(15px, 4px);
    right: round(nearest, 15px, 4px);
    bottom: round(up, 15px, 7px);
    left: round(down, 15px, 4px);
    width: round(to-zero, 15px, 4px);
}

/* becomes */

.test-functions {
    padding: 8px calc(3px) 1px calc(calc(3px) + 50%);
    transform: rotate(calc(-50deg));
    top: calc(16px);
    right: calc(16px);
    bottom: calc(21px);
    left: calc(12px);
    width: calc(12px);
}

Usage

Add PostCSS Stepped Value Functions to your project:

npm install postcss @csstools/postcss-stepped-value-functions --save-dev

Use it as a PostCSS plugin:

const postcss = require('postcss');
const postcssSteppedValueFunctions = require('@csstools/postcss-stepped-value-functions');

postcss([
    postcssSteppedValueFunctions(/* pluginOptions */)
]).process(YOUR_CSS /*, processOptions */);

⚠️ About custom properties

Given the dynamic nature of custom properties it's impossible to know what the variable value is, which means the plugin can't compute a final value for the stylesheet.

Because of that, any usage that contains a var is skipped.

Options

preserve

The preserve option determines whether the original notation is preserved. By default, it is not preserved.

postcssSteppedValueFunctions({ preserve: true })

.test-functions {
    padding: 8px mod(18px, 5px) 1px calc(rem(15px, 6px) + 50%);
    transform: rotate(mod(-140deg, -90deg));
    top: round(15px, 4px);
    right: round(nearest, 15px, 4px);
    bottom: round(up, 15px, 7px);
    left: round(down, 15px, 4px);
    width: round(to-zero, 15px, 4px);
}

/* becomes */

.test-functions {
    padding: 8px calc(3px) 1px calc(calc(3px) + 50%);
    padding: 8px mod(18px, 5px) 1px calc(rem(15px, 6px) + 50%);
    transform: rotate(calc(-50deg));
    transform: rotate(mod(-140deg, -90deg));
    top: calc(16px);
    top: round(15px, 4px);
    right: calc(16px);
    right: round(nearest, 15px, 4px);
    bottom: calc(21px);
    bottom: round(up, 15px, 7px);
    left: calc(12px);
    left: round(down, 15px, 4px);
    width: calc(12px);
    width: round(to-zero, 15px, 4px);
}