PostCSS Stepped Value Functions

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

.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 3px 1px calc(3px + 50%);
    transform: rotate(-50deg);
    top: 16px;
    right: 16px;
    bottom: 21px;
    left: 12px;
    width: 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 */);

PostCSS Stepped Value Functions runs in all Node environments, with special instructions for:

Node	PostCSS CLI	Webpack	Create React App	Gulp	Grunt

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

onInvalid

onInvalid option allows you to assign the warn value so you can get warnings when the usage of the functions is wrong.

postcssSteppedValueFunctions({ onInvalid: 'warn' })

.invalid {
    font-size: mod(18px, 5rem);
}

Will produce on the terminal:

[postcss-stepped-value-functions]: Failed to transform mod(18px, 5rem) as the units don't match