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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]
[![Support Chat][git-img]][git-url]
[PostCSS Calc] lets you reduce `calc()` references whenever it's possible.
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
```
Using this `input.css`:
```css
h1 {
font-size: calc(16px * 2);
height: calc(100px - 2em);
width: calc(2*var(--base-width));
margin-bottom: calc(16px * 1.5);
}
```
you will get:
```css
h1 {
font-size: 32px;
height: calc(100px - 2em);
width: calc(2*var(--base-width));
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;
}
```
---
## Related PostCSS plugins
To replace the value of CSS custom properties at build time, try [PostCSS Custom Properties].
## 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)
[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
|
