PostCSS plugin to reduce calc().

Particularly useful with the postcss-custom-properties

npm install postcss-calc

var postcss = require("postcss")
var calc = require("postcss-calc")

var css = postcss()
  .use(calc())
  .process(cssString)
  .css

This reduce calc() references whenever it's possible. This can be particularly useful with the postcss-custom-properties plugin.

Note: When multiple units are mixed together in the same expression, the calc() statement is left as is, to fallback to the w3c calc() feature.

Example (with postcss-custom-properties enabled as well):

// dependencies
var fs = require("fs")
var postcss = require("postcss")
var customProperties = require("postcss-custom-properties")
var calc = require("postcss-calc")

// css to be processed
var css = fs.readFileSync("style.css", "utf8")

var output = postcss()
  .use(customProperties())
  .use(calc())
  .process(css)
  .css

:root {
  --main-font-size: 16px;
}

body {
  font-size: var(--main-font-size);
}

h1 {
  font-size: calc(var(--main-font-size) * 2);
  height: calc(100px - 2em);
}

yields:

body {
  font-size: 16px
}

h1 {
  font-size: 32px;
  height: calc(100px - 2em)
}

See unit tests for a better example.

Work on a branch, install dev-dependencies, respect coding style & run tests before submitting a bug fix or a feature.

git clone https://github.com/postcss/postcss-calc.git
git checkout -b patch-1
npm install
npm test