A pure JavaScript implementation of Sass. Sass makes CSS fun again.

This package is a distribution of Dart Sass, compiled to pure JavaScript
with no native code or external dependencies. It provides a command-line sass
executable and a Node.js API.

• Usage
• API
• See Also
• Behavioral Differences from Ruby Sass

Usage

You can install Sass globally using npm install -g sass which will provide
access to the sass executable. You can also add it to your project using
npm install --save-dev sass. This provides the executable as well as a
library:

 var sass = require('sass');

sass.render({file: scss_filename}, function(err, result) { /* ... */ });

// OR

var result = sass.renderSync({file: scss_filename});

See below for details on Dart Sass's JavaScript API.

API

When installed via npm, Dart Sass supports a JavaScript API that's fully
compatible with Node Sass (with a few exceptions listed below), with support
for both the render() and renderSync() functions. See the Sass
website for full API documentation!

Note however that by default, renderSync() is more than twice as fast as
render() due to the overhead of asynchronous callbacks. To avoid this
performance hit, render() can use the fibers package to call
asynchronous importers from the synchronous code path. To enable this, pass the
Fiber class to the fiber option:

 var sass = require("sass");
var Fiber = require("fibers");

sass.render({
  file: "input.scss",
  importer: function(url, prev, done) {
    // ...
  },
  fiber: Fiber
}, function(err, result) {
  // ...
});

Both render() and renderSync() support the following options:

• data
• file
• functions
• importer
• includePaths
• indentType
• indentWidth
• indentedSyntax
• linefeed
• omitSourceMapUrl
• outFile
• sourceMapContents
• sourceMapEmbed
• sourceMapRoot
• sourceMap
• Only the "expanded" and "compressed" values of
  outputStyle are supported.

No support is intended for the following options:

• precision. Dart Sass defaults
  to a sufficiently high precision for all existing browsers, and making this
  customizable would make the code substantially less efficient.

• sourceComments. Source
  maps are the recommended way of locating the origin of generated selectors.

See Also

• Dart Sass, from which this package is compiled, can be used either as a
  stand-alone executable or as a Dart library. Running Dart Sass on the Dart VM
  is substantially faster than running the pure JavaScript version, so this may
  be appropriate for performance-sensitive applications. The Dart API is also
  (currently) more user-friendly than the JavaScript API. See
  the Dart Sass README for details on how to use it.

• Node Sass, which is a wrapper around LibSass, the C++ implementation
  of Sass. Node Sass supports the same API as this package and is also faster
  (although it's usually a little slower than Dart Sass). However, it requires a
  native library which may be difficult to install, and it's generally slower to
  add features and fix bugs.

Behavioral Differences from Ruby Sass

There are a few intentional behavioral differences between Dart Sass and Ruby
Sass. These are generally places where Ruby Sass has an undesired behavior, and
it's substantially easier to implement the correct behavior than it would be to
implement compatible behavior. These should all have tracking bugs against Ruby
Sass to update the reference behavior.

1. @extend only accepts simple selectors, as does the second argument of
   selector-extend(). See issue 1599.

2. Subject selectors are not supported. See issue 1126.

3. Pseudo selector arguments are parsed as <declaration-value>s rather than
   having a more limited custom parsing. See issue 2120.

4. The numeric precision is set to 10. See issue 1122.

5. The indented syntax parser is more flexible: it doesn't require consistent
   indentation across the whole document. See issue 2176.

6. Colors do not support channel-by-channel arithmetic. See issue 2144.

7. Unitless numbers aren't == to unit numbers with the same value. In
   addition, map keys follow the same logic as ==-equality. See
   issue 1496.

8. rgba() and hsla() alpha values with percentage units are interpreted as
   percentages. Other units are forbidden. See issue 1525.

9. Too many variable arguments passed to a function is an error. See
   issue 1408.

10. Allow @extend to reach outside a media query if there's an identical
    @extend defined outside that query. This isn't tracked explicitly, because
    it'll be irrelevant when issue 1050 is fixed.

11. Some selector pseudos containing placeholder selectors will be compiled
    where they wouldn't be in Ruby Sass. This better matches the semantics of
    the selectors in question, and is more efficient. See issue 2228.

12. The old-style :property value syntax is not supported in the indented
    syntax. See issue 2245.

13. The reference combinator is not supported. See issue 303.

14. Universal selector unification is symmetrical. See issue 2247.

15. @extend doesn't produce an error if it matches but fails to unify. See
    issue 2250.

16. Dart Sass currently only supports UTF-8 documents. We'd like to support
    more, but Dart currently doesn't support them. See dart-lang/sdk#11744,
    for example.

Disclaimer: this is not an official Google product.