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- # PostCSS Calc [<img src="https://postcss.github.io/postcss/logo.svg" alt="PostCSS" width="90" height="90" align="right">][PostCSS]
- [![NPM Version][npm-img]][npm-url]
- [![Build Status][cli-img]][cli-url]
- [![Support Chat][git-img]][git-url]
- [PostCSS Calc] lets you reduce `calc()` references whenever it's possible. This
- can be particularly useful with the [PostCSS Custom Properties] plugin.
- When multiple units are mixed together in the same expression, the `calc()`
- statement is left as is, to fallback to the [W3C calc() implementation].
- ## Installation
- ```bash
- npm install postcss-calc
- ```
- ## Usage
- ```js
- // dependencies
- var fs = require("fs")
- var postcss = require("postcss")
- var calc = require("postcss-calc")
- // css to be processed
- var css = fs.readFileSync("input.css", "utf8")
- // process css
- var output = postcss()
- .use(calc())
- .process(css)
- .css
- ```
- **Example** (with [PostCSS Custom Properties] enabled as well):
- ```js
- // 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("input.css", "utf8")
- // process css
- var output = postcss()
- .use(customProperties())
- .use(calc())
- .process(css)
- .css
- ```
- Using this `input.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);
- margin-bottom: calc(
- var(--main-font-size)
- * 1.5
- )
- }
- ```
- you will get:
- ```css
- body {
- font-size: 16px
- }
- h1 {
- font-size: 32px;
- height: calc(100px - 2em);
- margin-bottom: 24px
- }
- ```
- Checkout [tests] for more examples.
- ### Options
- #### `precision` (default: `5`)
- Allow you to define the precision for decimal numbers.
- ```js
- var out = postcss()
- .use(calc({precision: 10}))
- .process(css)
- .css
- ```
- #### `preserve` (default: `false`)
- Allow you to preserve calc() usage in output so browsers will handle decimal
- precision themselves.
- ```js
- var out = postcss()
- .use(calc({preserve: true}))
- .process(css)
- .css
- ```
- #### `warnWhenCannotResolve` (default: `false`)
- Adds warnings when calc() are not reduced to a single value.
- ```js
- var out = postcss()
- .use(calc({warnWhenCannotResolve: true}))
- .process(css)
- .css
- ```
- #### `mediaQueries` (default: `false`)
- Allows calc() usage as part of media query declarations.
- ```js
- var out = postcss()
- .use(calc({mediaQueries: true}))
- .process(css)
- .css
- ```
- #### `selectors` (default: `false`)
- Allows calc() usage as part of selectors.
- ```js
- var out = postcss()
- .use(calc({selectors: true}))
- .process(css)
- .css
- ```
- Example:
- ```css
- div[data-size="calc(3*3)"] {
- width: 100px;
- }
- ```
- ---
- ## Contributing
- Work on a branch, install dev-dependencies, respect coding style & run tests
- before submitting a bug fix or a feature.
- ```bash
- git clone git@github.com:postcss/postcss-calc.git
- git checkout -b patch-1
- npm install
- npm test
- ```
- ## [Changelog](CHANGELOG.md)
- ## [License](LICENSE)
- [cli-img]: https://img.shields.io/travis/postcss/postcss-calc/master.svg
- [cli-url]: https://travis-ci.org/postcss/postcss-calc
- [git-img]: https://img.shields.io/badge/support-chat-blue.svg
- [git-url]: https://gitter.im/postcss/postcss
- [npm-img]: https://img.shields.io/npm/v/postcss-calc.svg
- [npm-url]: https://www.npmjs.com/package/postcss-calc
- [PostCSS]: https://github.com/postcss
- [PostCSS Calc]: https://github.com/postcss/postcss-calc
- [PostCSS Custom Properties]: https://github.com/postcss/postcss-custom-properties
- [tests]: src/__tests__/index.js
- [W3C calc() implementation]: https://www.w3.org/TR/css3-values/#calc-notation
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