node-sass

What is node-sass?

The node-sass npm package is a library that allows you to natively compile .scss files to CSS at incredible speed and automatically via a connect middleware. It provides a binding for Node.js to the Sass engine, which is written in C++ and allows for the translation of SCSS or SASS syntax into standard CSS that browsers can understand.

What are node-sass's main functionalities?

Compiling SCSS to CSS

This feature allows you to compile .scss files into .css files. The 'render' method takes an options object and a callback function. The options object specifies the input and output paths for the SCSS and CSS files, respectively. The callback is invoked after the compilation process, and you can handle the result or error accordingly.

const sass = require('node-sass');
sass.render({
  file: 'path/to/input.scss',
  outFile: 'path/to/output.css'
}, function(error, result) { // Node-style callback from v3.0.0 onwards
  if(!error){
    // No errors during the compilation, write this result on the disk
    fs.writeFile('path/to/output.css', result.css, function(err){
      if(!err){
        //file written on disk
      }
    });
  }
});

Watching files or directories

This feature allows you to watch .scss files or directories for changes and automatically recompile them to CSS when a change is detected. The example uses 'chokidar', an external library for watching files, to listen for changes on the specified SCSS file and then uses node-sass to compile the file to CSS.

const sass = require('node-sass');
const chokidar = require('chokidar');

chokidar.watch('path/to/input.scss').on('change', () => {
  sass.render({
    file: 'path/to/input.scss',
    outFile: 'path/to/output.css'
  }, function(error, result) {
    if (!error) {
      fs.writeFile('path/to/output.css', result.css, function(err){
        if(!err){
          console.log('SCSS file updated.');
        }
      });
    }
  });
});

Command Line Interface (CLI) usage

node-sass provides a CLI for compiling SCSS files to CSS directly from the command line. In this example, the '--output-style' option is used to specify the CSS output format (compressed in this case), '-o' is used to define the output directory for the compiled CSS, and the last argument is the input directory containing the SCSS files.

node-sass --output-style compressed -o dist/css src/scss

Other packages similar to node-sass

sass

The 'sass' package is the primary implementation of Sass, which is written in Dart. It provides the same core functionality as node-sass but does not rely on a native C++ binding, making it more portable and easier to install across different environments. It is also the package recommended by the Sass team as node-sass has been deprecated.

postcss

PostCSS is a tool for transforming CSS with JavaScript plugins. While it is not a direct replacement for node-sass, it can be used with plugins like 'precss' to provide similar SCSS-like syntax and features. PostCSS is highly extensible and can be integrated with a large number of plugins to extend its capabilities beyond what node-sass offers.

less

Less is a backward-compatible language extension for CSS. It is similar to SCSS in terms of features like variables, mixins, and nesting, but it has its own syntax and compiles to CSS using the Less compiler. While it serves a similar purpose to node-sass, it is a different preprocessor language with its own community and ecosystem.

stylus

Stylus is a preprocessor that serves as an alternative to SCSS. It offers a flexible syntax with optional colons, semicolons, and braces, and provides powerful features like variable interpolation and functions. Stylus can be seen as a more expressive, but less widely adopted, alternative to node-sass.

README

node-sass

Node-sass is a library that provides binding for Node.js to libsass, the C version of the popular stylesheet preprocessor, Sass.

It allows you to natively compile .scss files to css at incredible speed and automatically via a connect middleware.

Find it on npm: https://npmjs.org/package/node-sass

Follow @nodesass on twitter for release updates: https://twitter.com/nodesass

Install

npm install node-sass

Some users have reported issues installing on Ubuntu due to node being registered to another package. Follow the official NodeJS docs to install NodeJS so that #!/usr/bin/env node correctly resolved.

Compiling versions 0.9.4 and above on Windows machines requires Visual Studio 2013 WD. If you have multiple VS versions, use npm install with the --msvs_version=2013 flag also use this flag when rebuilding the module with node-gyp or nw-gyp.

Usage

var sass = require('node-sass');
sass.render({
  file: scss_filename,
  [, options..]
}, function(err, result) { /*...*/ });
// OR
var result = sass.renderSync({
  data: scss_content
  [, options..]
});

Options

file

Type: String | null Default: null Special: file or data must be specified

Path to a file for libsass to render.

data

Type: String | null Default: null Special: file or data must be specified

A string to pass to libsass to render. It is recommended that you use includePaths in conjunction with this so that libsass can find files when using the @import directive.

importer (>= v2.0.0)

Type: Function signature function(url, prev, done) Default: undefined

Function Parameters and Information:

• url (String) - the path in import as-is, which libsass encountered
• prev (String) - the previously resolved path
• done (Function) - a callback function to invoke on async completion, takes an object literal containing
  • file (String) - an alternate path for libsass to use OR
  • contents (String) - the imported contents (for example, read from memory or the file system)

Handles when libsass encounters the @import directive. A custom importer allows extension of the libsass engine in both a synchronous and asynchronous manner. In both cases, the goal is to either return or call done() with an object literal. Depending on the value of the object literal, one of two things will happen.

When returning or calling done() with { file: "String" }, the new file path will be assumed for the @import. It's recommended to be mindful of the value of prev in instances where relative path resolution may be required.

When returning or calling done() with { contents: "String" }, the string value will be used as if the file was read in through an external source.

Starting from v3.0.0, this refers to a contextual scope for the immediate run of sass.render or sass.renderSync

functions (>= v3.0.0)

functions is an Object that holds a collection of custom functions that may be invoked by the sass files being compiled. They may take zero or more input parameters and must return a value either synchronously (return ...;) or asynchronously (done();). Those parameters will be instances of one of the constructors contained in the require('node-sass').types hash. The return value must be of one of these types as well. See the list of available types below:

types.Number(value [, unit = ""])

• getValue()/ setValue(value) : gets / sets the numerical portion of the number
• getUnit() / setUnit(unit) : gets / sets the unit portion of the number

types.String(value)

• getValue() / setValue(value) : gets / sets the enclosed string

types.Color(r, g, b [, a = 1.0]) or types.Color(argb)

• getR() / setR(value) : red component (integer from 0 to 255)
• getG() / setG(value) : green component (integer from 0 to 255)
• getB() / setB(value) : blue component (integer from 0 to 255)
• getA() / setA(value) : alpha component (number from 0 to 1.0)

Example:

var Color = require('node-sass').types.Color,
  c1 = new Color(255, 0, 0),
  c2 = new Color(0xff0088cc);

types.Boolean(value)

• getValue() : gets the enclosed boolean
• types.Boolean.TRUE : Singleton instance of types.Boolean that holds "true"
• types.Boolean.FALSE : Singleton instance of types.Boolean that holds "false"

types.List(length [, commaSeparator = true])

• getValue(index) / setValue(index, value) : value must itself be an instance of one of the constructors in sass.types.
• getSeparator() / setSeparator(isComma) : whether to use commas as a separator
• getLength()

types.Map(length)

• getKey(index) / setKey(index, value)
• getValue(index) / setValue(index, value)
• getLength()

types.Null()

• types.Null.NULL : Singleton instance of types.Null.

Example

sass.renderSync({
  data: '#{headings(2,5)} { color: #08c; }',
  functions: {
    'headings($from: 0, $to: 6)': function(from, to) {
      var i, f = from.getValue(), t = to.getValue(),
          list = new sass.types.List(t - f + 1);

      for (i = f; i <= t; i++) {
        list.setValue(i - f, new sass.types.String('h' + i));
      }

      return list;
    }
  }
});

includePaths

Type: Array<String> Default: []

An array of paths that libsass can look in to attempt to resolve your @import declarations. When using data, it is recommended that you use this.

indentedSyntax

Type: Boolean Default: false

true values enable Sass Indented Syntax for parsing the data string or file.

indentType (>= v3.0.0)

Type: String Default: space

Used to determine whether to use space or tab character for indentation.

indentWidth (>= v3.0.0)

Type: Number Default: 2 Maximum: 10

Used to determine the number of spaces or tabs to be used for indentation.

linefeed (>= v3.0.0)

Type: String Default: lf

Used to determine whether to use cr, crlf, lf or lfcr sequence for line break.

omitSourceMapUrl

Type: Boolean Default: false Special: When using this, you should also specify outFile to avoid unexpected behavior.

true values disable the inclusion of source map information in the output file.

outFile

Type: String | null Default: null Special: Required when sourceMap is a truthy value

Specify the intended location of the output file. Strongly recommended when outputting source maps so that they can properly refer back to their intended files.

outputStyle

Type: String Default: nested Values: nested, compressed

Determines the output format of the final CSS style. ('expanded' and 'compact' are not currently supported by libsass, but are planned in a future version.)

precision

Type: Integer Default: 5

Used to determine how many digits after the decimal will be allowed. For instance, if you had a decimal number of 1.23456789 and a precision of 5, the result will be 1.23457 in the final CSS.

sourceComments

Type: Boolean Default: false

true enables additional debugging information in the output file as CSS comments

sourceMap

Type: Boolean | String | undefined Default: undefined Special: Setting the sourceMap option requires also setting the outFile option

Enables the outputting of a source map during render and renderSync. When sourceMap === true, the value of outFile is used as the target output location for the source map. When typeof sourceMap === "String", the value of sourceMap will be used as the writing location for the file.

sourceMapEmbed

Type: Boolean Default: false

true embeds the source map as a data URI

sourceMapContents

Type: Boolean Default: false

true includes the contents in the source map information

render Callback (>= v3.0.0)

node-sass supports standard node style asynchronous callbacks with the signature of function(err, result). In error conditions, the error argument is populated with the error object. In success conditions, the result object is populated with an object describing the result of the render call.

Error Object

• message (String) - The error message.
• line (Number) - The line number of error.
• column (Number) - The column number of error.
• status (Number) - The status code.
• file (String) - The filename of error. In case file option was not set (in favour of data), this will reflect the value stdin.

Result Object

• css (Buffer) - The compiled CSS. Write this to a file, or serve it out as needed.
• map (Buffer) - The source map
• stats (Object) - An object containing information about the compile. It contains the following keys:
  • entry (String) - The path to the scss file, or data if the source was not a file
  • start (Number) - Date.now() before the compilation
  • end (Number) - Date.now() after the compilation
  • duration (Number) - end - start
  • includedFiles (Array) - Absolute paths to all related scss files in no particular order.

Examples

var sass = require('node-sass');
sass.render({
  file: '/path/to/myFile.scss',
  data: 'body{background:blue; a{color:black;}}',
  importer: function(url, prev, done) {
    // url is the path in import as is, which libsass encountered.
    // prev is the previously resolved path.
    // done is an optional callback, either consume it or return value synchronously.
    // this.options contains this options hash, this.callback contains the node-style callback
    someAsyncFunction(url, prev, function(result){
      done({
        file: result.path, // only one of them is required, see section Sepcial Behaviours.
        contents: result.data
      });
    });
    // OR
    var result = someSyncFunction(url, prev);
    return {file: result.path, contents: result.data};
  },
  includePaths: [ 'lib/', 'mod/' ],
  outputStyle: 'compressed'
}, function(error, result) { // node-style callback from v3.0.0 onwards
  if (error) {
    console.log(error.status); // used to be "code" in v2x and below
    console.log(error.column);
    console.log(error.message);
    console.log(error.line);
  }
  else {
    console.log(result.css.toString());

    console.log(result.stats);

    console.log(result.map.toString());
    // or better
    console.log(JSON.stringify(result.map)); // note, JSON.stringify accepts Buffer too
  }
});
// OR
var result = sass.renderSync({
  file: '/path/to/file.scss',
  data: 'body{background:blue; a{color:black;}}',
  outputStyle: 'compressed',
  outFile: '/to/my/output.css',
  sourceMap: true, // or an absolute or relative (to outFile) path
  importer: function(url, prev, done) {
    // url is the path in import as is, which libsass encountered.
    // prev is the previously resolved path.
    // done is an optional callback, either consume it or return value synchronously.
    // this.options contains this options hash
    someAsyncFunction(url, prev, function(result){
      done({
        file: result.path, // only one of them is required, see section Sepcial Behaviours.
        contents: result.data
      });
    });
    // OR
    var result = someSyncFunction(url, prev);
    return {file: result.path, contents: result.data};
  },
}));

console.log(result.css);
console.log(result.map);
console.log(result.stats);

Special behaviours

• In the case that both file and data options are set, node-sass will give precedence to data and use file to calculate paths in sourcemaps.

Version information (>= v2.0.0)

Both node-sass and libsass version info is now present in package.json and is exposed via info method:

var sass = require('node-sass');

console.log(sass.info);

/*
  it will output something like:

  node-sass       2.0.1   (Wrapper)       [JavaScript]
  libsass         3.1.0   (Sass Compiler) [C/C++]
*/

Integrations

Listing of community uses of node-sass in build tools and frameworks.

Brackets extension

@jasonsanjose has created a Brackets extension based on node-sass: https://github.com/jasonsanjose/brackets-sass. When editing Sass files, the extension compiles changes on save. The extension also integrates with Live Preview to show Sass changes in the browser without saving or compiling.

Brunch plugin

Brunch's official sass plugin uses node-sass by default, and automatically falls back to ruby if use of Compass is detected: https://github.com/brunch/sass-brunch

Connect/Express middleware

Recompile .scss files automatically for connect and express based http servers.

This functionality has been moved to node-sass-middleware in node-sass v1.0.0

DocPad Plugin

@jking90 wrote a DocPad plugin that compiles .scss files using node-sass: https://github.com/jking90/docpad-plugin-nodesass

Duo.js extension

@stephenway has created an extension that transpiles Sass to CSS using node-sass with duo.js https://github.com/duojs/sass

Grunt extension

@sindresorhus has created a set of grunt tasks based on node-sass: https://github.com/sindresorhus/grunt-sass

Gulp extension

@dlmanning has created a gulp sass plugin based on node-sass: https://github.com/dlmanning/gulp-sass

Harp

@sintaxi’s Harp web server implicitly compiles .scss files using node-sass: https://github.com/sintaxi/harp

Metalsmith plugin

@stevenschobert has created a metalsmith plugin based on node-sass: https://github.com/stevenschobert/metalsmith-sass

Meteor plugin

@fourseven has created a meteor plugin based on node-sass: https://github.com/fourseven/meteor-scss

Mimosa module

@dbashford has created a Mimosa module for sass which includes node-sass: https://github.com/dbashford/mimosa-sass

Example App

There is also an example connect app here: https://github.com/andrew/node-sass-example

Rebuilding binaries

Node-sass includes pre-compiled binaries for popular platforms, to add a binary for your platform follow these steps:

Check out the project:

git clone --recursive https://github.com/sass/node-sass.git
cd node-sass
git submodule update --init --recursive
npm install
node scripts/build -f  # use -d switch for debug release
# if succeeded, it will generate and move
# the binary in vendor directory.

Command Line Interface

The interface for command-line usage is fairly simplistic at this stage, as seen in the following usage section.

Output will be saved with the same name as input SASS file into the current working directory if it's omitted.

Usage

node-sass [options] <input.scss> [output.css] cat <input.scss> | node-sass > output.css

Options:

    -w, --watch                Watch a directory or file
    -r, --recursive            Recursively watch directories or files
    -o, --output               Output directory
    -x, --omit-source-map-url  Omit source map URL comment from output
    -i, --indented-syntax      Treat data from stdin as sass code (versus scss)
    -v, --version              Prints version info
    --output-style             CSS output style (nested | expanded | compact | compressed)
    --indent-type              Indent type for output CSS (space | tab)
    --indent-width             Indent width; number of spaces or tabs (maximum value: 10)
    --linefeed                 Linefeed style (cr | crlf | lf | lfcr)
    --source-comments          Include debug info in output
    --source-map               Emit source map
    --source-map-embed         Embed sourceMappingUrl as data URI
    --source-map-contents      Embed include contents in map
    --include-path             Path to look for imported files
    --precision                The amount of precision allowed in decimal numbers
    --importer                 Path to custom importer
    --help                     Print usage info

Note --importer takes the (absolute or relative to pwd) path to a js file, which needs to have a default module.exports set to the importer function. See our test fixtures for example.

Post-install Build

Install runs only two Mocha tests to see if your machine can use the pre-built libsass which will save some time during install. If any tests fail it will build from source.

Maintainers

This module is brought to you and maintained by the following people:

• Adeel Mujahid - Project Lead (Github / Twitter)
• Andrew Nesbitt (Github / Twitter)
• Dean Mao (Github / Twitter)
• Brett Wilkins (Github / Twitter)
• Keith Cirkel (Github / Twitter)
• Laurent Goderre (Github / Twitter)
• Nick Schonning (Github / Twitter)
• Adam Yeats (Github / Twitter)

Contributors

We <3 our contributors! A special thanks to all those who have clocked in some dev time on this project, we really appreciate your hard work. You can find a full list of those people here.

Note on Patches/Pull Requests

• Fork the project.
• Make your feature addition or bug fix.
• Add documentation if necessary.
• Add tests for it. This is important so I don't break it in a future version unintentionally.
• Send a pull request. Bonus points for topic branches.

Copyright

Copyright (c) 2015 Andrew Nesbitt. See LICENSE for details.