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Compile your LESS stylesheets using JSON and underscore.

assemble-styles v0.2.0 Build Status

Compile your LESS stylesheets using underscore and JSON.

The project is current and under active development. We welcome contributions!

Table of Contents

Getting Started

This plugin requires Grunt ~0.4.0

If you haven't used Grunt before, be sure to check out the Getting Started guide, as it explains how to create a Gruntfile as well as install and use Grunt plugins. Once you're familiar with that process, you may install this plugin with this command:

npm install assemble-styles --save-dev

Once the plugin has been installed, it may be enabled inside your Gruntfile with this line of JavaScript:


This plugin was designed to work with Grunt 0.4.x. If you're still using grunt v0.3.x it's strongly recommended that you upgrade, but in case you can't please use v0.3.2.

Styles task

Run this task with the grunt styles command.

Task targets, files and options may be specified according to the grunt Configuring tasks guide. ### Options


Type: String|Array Default: empty string

Specified files will be prepended to the beginning of src files, not to the concatenated output. This feature is useful for "inlining" globaly-required LESS files, such as variables.less and mixins.less, so that they do not need to be referenced with @import statements inside any individual files.


Type: Boolean Default: true

Concatenate all source files by default. If you change the value to false, all source files will compile into individual files.


Type: String|Array Default: Directory of input file.

Specifies directories to scan for @import directives when parsing. Default value is the directory of the source, which is probably what you want. In other words, the paths option allows you to specify paths for your @import statements in the styles task, as an alternative to specifying a path on every @import statement that appears throughout your LESS files. So instead of doing this:

@import "path/to/my/less/files/mixins/mixins.less";
@import "path/to/my/less/files/bootstrap.less";
@import "path/to/my/custom/less/files/somewhere/else/custom.less";

you can do this:

@import "mixins.less";
@import "bootstrap.less";
@import "custom.less";


Type: Boolean Default: False

Compress output by removing some whitespaces.


Type: Boolean Default: False

Compress output using cssmin.js


Type: Integer Default: null

Set the parser's optimization level. The lower the number, the less nodes it will create in the tree. This could matter for debugging, or if you want to access the individual nodes in the tree.


Type: Boolean Default: False

Force evaluation of imports.


Type: String Default: false

Configures -sass-debug-info support.

Accepts following values: comments, mediaquery, all.

Usage Examples

Default Options

In your project's Gruntfile, add a section named styles to the data object passed into grunt.initConfig().

  styles: {
    options: {},
    files: {
      'path/to/result.css': ['path/to/source.less']

Custom Options

In this example, the paths and requires options are used:

styles: {
  development: {
    options: {
      paths: ['src/less/files/'],
      requires: [
    files: {
      'dest/compiled.css': ['src/source.less']
  production: {
    options: {
      paths: ['assets/css'],
      yuicompress: true
    files: {
      'dest/compiled.css': ['src/less/source.less']

Twitter Bootstrap

Pick and choose which Bootstrap components you want to "bundle" or exclude.

A common (unjustified) complaint about Bootstrap is that it's bloated or has too many "extras", which really means: "it's too much work to comment out or remove the @import statements I'm not using".

Well, lazy people rejoice! Because assemble-styles makes it easier than squeeze cheeze to customize Bootstrap.

(See bootstrap.json).

styles: {
  // Global task options. These can also be set for each target. 
  options: {
    paths:    ['<%= bootstrap.base %>'],
    requires: '<%= bootstrap.less.globals %>'
  // Compile bootstrap.less 
  bootstrap: {
    src:  '<%= bootstrap.lib %>',
    dest: 'examples/css/bootstrap.css'
  // Compile LESS "bundles" specified in ./examples/bootstrap.json 
  core: {
    src:  '<%= bootstrap.less.core %>',
    dest: 'examples/css/core.css'
  common: {
    src:  '<%= bootstrap.less.common %>',
    dest: 'examples/css/common.css'
  nav: {
    src:  '<%= bootstrap.less.nav %>',
    dest: 'examples/css/nav.css'
  zindex: {
    src:  '<%= bootstrap.less.zindex %>',
    dest: 'examples/css/zindex.css'
  misc: {
    src:  '<%= bootstrap.less.misc %>',
    dest: 'examples/css/misc.css'
  utilities: {
    src:  '<%= bootstrap.less.util %>',
    dest: 'examples/css/utilities.css'
  // Compile a single component 
  single: {
    options: {concat: false },
    src:  '<%= bootstrap.less.alerts %>',
    dest: 'examples/css/single'
  // Compile LESS files individually 
  individual: {
    options: {
      concat: false
    src:  '<%= bootstrap.less.all %>',
    dest: 'examples/css/individual'
  // Compile LESS files individually, using minimatch pattern 
  each: {
    options: {
      concat: false
    src:  ['examples/less/bootstrap/**/*.less'],
    dest: 'examples/css/individual'
  // bootstrap.less is ignored 
  ignored: {
    options: {
      concat: false
    src:  ['<%= bootstrap.less.core %>', '!examples/less/bootstrap/bootstrap.less'],
    dest: 'examples/css/individual'


assemble-styles is a gruntplugin for compiling LESS to CSS, but with a twist that you won't find in other similar plugins. This plugin makes it much easier to maintain libraries of LESS components and themes, by leveraging JSON and underscore templates to enable you to define LESS "packages" or "bundles" using external configuration files.

The plugin is quite simple to use, and it demonstrates good conventions for managing your LESS components. But the best part is that you can easily switch back and forth between:

  • compiling your LESS components individually, o
  • concatentating all of your LESS files into a singe file

The best part is that your LESS projects will be easier to maintain.


In lieu of a formal styleguide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint and test your code using Grunt.


assemble-styles, and some of the documentation on this page, is derived from grunt-contrib-less, authored by Tyler Kellen. The plugin was modified to concat LESS files first, and then compile them into CSS files. This allows for prepending globally required LESS files, and it also adds the ability to build out individual CSS files, rathers than building a single conctatenated file.

Release History

  • 2013-03-12   v0.2.0   Travis CI
  • 2013-03-08   v0.1.7   Many task improvements, enhanced bootstrap.json model. Greatly improved examples, readme updates.
  • 2013-02-27   v0.1.2   Add support for concat and requires options.
  • 2013-02-27   v0.1.0   First commit.

Task submitted by Brian Woodward

This file was generated on Fri March 8 2013.