138 lines
3.7 KiB
Markdown
138 lines
3.7 KiB
Markdown
# PostCSS Environment Variables [<img src="https://postcss.github.io/postcss/logo.svg" alt="PostCSS Logo" width="90" height="90" align="right">][postcss]
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[![NPM Version][npm-img]][npm-url]
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[![CSS Standard Status][css-img]][css-url]
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[![Build Status][cli-img]][cli-url]
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[![Support Chat][git-img]][git-url]
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[PostCSS Environment Variables] lets you use `env()` variables in CSS,
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following the [CSS Environment Variables] specification.
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```pcss
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@media (max-width: env(--branding-small)) {
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body {
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padding: env(--branding-padding);
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}
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}
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/* becomes */
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@media (min-width: 600px) {
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body {
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padding: 20px;
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}
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}
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/* when the `importFrom` option is: {
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"environmentVariables": {
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"--branding-small": "600px",
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"--branding-padding": "20px"
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}
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} */
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```
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## Usage
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Add [PostCSS Environment Variables] to your project:
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```bash
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npm install postcss-env-function --save-dev
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```
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Use [PostCSS Environment Variables] to process your CSS:
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```js
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const postcssEnvFunction = require('postcss-env-function');
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postcssEnvFunction.process(YOUR_CSS /*, processOptions, pluginOptions */);
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```
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Or use it as a [PostCSS] plugin:
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```js
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const postcss = require('postcss');
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const postcssEnvFunction = require('postcss-env-function');
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postcss([
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postcssEnvFunction(/* pluginOptions */)
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]).process(YOUR_CSS /*, processOptions */);
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```
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[PostCSS Environment Variables] runs in all Node environments, with special instructions for:
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| [Node](INSTALL.md#node) | [PostCSS CLI](INSTALL.md#postcss-cli) | [Webpack](INSTALL.md#webpack) | [Create React App](INSTALL.md#create-react-app) | [Gulp](INSTALL.md#gulp) | [Grunt](INSTALL.md#grunt) |
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| --- | --- | --- | --- | --- | --- |
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## Options
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### importFrom
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The `importFrom` option specifies sources where Environment Variables can be
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imported from, which might be JS and JSON files, functions, and directly passed
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objects.
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```js
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postcssCustomProperties({
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importFrom: 'path/to/file.js' /* module.exports = {
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environmentVariables: {
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'--branding-padding': '20px',
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'--branding-small': '600px'
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}
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} */
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});
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```
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```pcss
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@media (max-width: env(--branding-small)) {
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body {
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padding: env(--branding-padding);
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}
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}
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/* becomes */
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@media (min-width: 600px) {
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body {
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padding: 20px;
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}
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}
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```
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Multiple sources can be passed into this option, and they will be parsed in the
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order they are received. JavaScript files, JSON files, functions, and objects
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will need to namespace Custom Properties using the `environmentVariables` or
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`variables-variables` key.
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```js
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postcssCustomProperties({
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importFrom: [
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'path/to/file.js', // module.exports = { environmentVariables: { '--branding-padding': '20px' } }
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'and/then/this.json', // { "environment-variables": { "--branding-padding": "20px" } }
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{
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environmentVariables: { '--branding-padding': '20px' }
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},
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() => {
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const environmentVariables = { '--branding-padding': '20px' };
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return { environmentVariables };
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}
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]
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});
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```
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See example imports written in [JS](test/import-variables.js) and
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[JSON](test/import-variables.json).
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[cli-img]: https://img.shields.io/travis/jonathantneal/postcss-env-function.svg
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[cli-url]: https://travis-ci.org/jonathantneal/postcss-env-function
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[css-img]: https://cssdb.org/badge/environment-variables.svg
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[css-url]: https://cssdb.org/#environment-variables
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[git-img]: https://img.shields.io/badge/support-chat-blue.svg
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[git-url]: https://gitter.im/postcss/postcss
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[npm-img]: https://img.shields.io/npm/v/postcss-env-function.svg
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[npm-url]: https://www.npmjs.com/package/postcss-env-function
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[CSS Environment Variables]: https://drafts.csswg.org/css-env-1/
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[PostCSS]: https://github.com/postcss/postcss
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[PostCSS Environment Variables]: https://github.com/jonathantneal/postcss-env-function
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