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# CSSJanus

Convert CSS stylesheets between left-to-right and right-to-left.

Based on the original [Google project](https://code.google.com/p/cssjanus/).

See **[Interactive demo](https://doc.wikimedia.org/cssjanus/master/)**.

## Install

```sh
npm install cssjanus
```

## Usage

```javascript
var cssjanus = require( 'cssjanus' );

// Example: convert LTR CSS to RTL
var ltrCss = 'body { margin-left: 10px; }';
var rtlCss = cssjanus.transform( ltrCss );

console.log( rtlCss );
// → body { margin-right: 10px; }
```

Signature:

```
transform( string css [, Object options ] ) : string
```

Parameters:

* `css` Stylesheet to transform
* `options`: Options object (optional)
 * `options.transformDirInUrl` (Boolean): Transform directions in URLs, such as `ltr` to `rtl`. Default: `false`.
 * `options.transformEdgeInUrl` (Boolean): Transform edges in URLs, such as `left` to `right`. Default: `false`.

### Preventing flipping

If a rule is not meant to be flipped by CSSJanus, use a `/* @noflip */` comment to protect the rule.

```css
.rule1 {
  /* Will be converted to margin-right */
  margin-left: 1em;
}
/* @noflip */
.rule2 {
  /* Will be preserved as margin-left */
  margin-left: 1em;
}
```

## CSS Logical

We encourage and recommend use of
[CSS logical properties](https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_logical_properties_and_values)
for the subset of CSS features where a native
direction-aware version of a CSS property exists
(be sure to check [browser support](https://caniuse.com/)
for specific properties). You can, for example, set
properties like `margin-inline-start` instead of
`margin-left`, which the browser flips based on content
direction, and work seamlessly alongside other CSS
properties that CSSJanus flips instead.

Note that CSS logical properties flip based on nearest
content direction and content language, whereas CSSJanus
is generally configured to flip by user language and
UI direction.

## Integrations

* **[css](https://www.npmjs.com/package/css)** parser: [rtl-converter](https://github.com/HosseinAlipour/rtl-converter).
* **Grunt**: [grunt-cssjanus](https://gerrit.wikimedia.org/g/mediawiki/tools/grunt-cssjanus).
* **PHP** port: [php-cssjanus](https://gerrit.wikimedia.org/g/mediawiki/libs/php-cssjanus/).
* **Gulp**: [gulp-cssjanus](https://github.com/tomyam1/gulp-cssjanus).
* **PostCSS**: [postcss-cssjanus](https://www.npmjs.com/package/postcss-janus).
* **styled-components**: [styled-components-rtl](https://www.npmjs.com/package/styled-components-rtl).
* **Stylis**: [stylis-plugin-rtl](https://www.npmjs.com/package/stylis-plugin-rtl).
* **webpack**: [cssjanus-webpack](https://www.npmjs.com/package/@mooeypoo/cssjanus-webpack), [webpack-arabic-css](https://www.npmjs.com/package/webpackarabiccssplugin).

## Who uses CSSJanus?

* **[Wikimedia Foundation](https://www.wikimedia.org/)**, the non-profit behind Wikipedia and other free knowledge projects. Used as part of [MediaWiki](https://www.mediawiki.org/wiki/MediaWiki) and [VisualEditor](https://gerrit.wikimedia.org/g/VisualEditor/VisualEditor) on [Wikipedia](https://ar.wikipedia.org/), and [more](https://doc.wikimedia.org/).
* **[WordPress](https://wordpress.org/)**, a free and open-source content management system. Used for the interface of wp-admin and the default yearly themes.
* **[styled-components](https://styled-components.com/)**, an ecosystem of visual primitives. Its RTL support is powered by CSSJanus.
* **[AdminLTE](https://adminlte.io/)**, an open-source admin dashboard and control panel theme. See
[AdminLTE-RTL](https://github.com/mmdsharifi/AdminLTE-RTL).

## See also

* [Interactive demo](https://cssjanus.github.io)

## Contribute

* Issue tracker: <https://phabricator.wikimedia.org/tag/cssjanus/>
* Source code: <https://gerrit.wikimedia.org/g/mediawiki/libs/node-cssjanus>
* Submit patches via Gerrit: <https://www.mediawiki.org/wiki/Developer_account>