grunt-contrib-less
Advanced tools
The grunt-contrib-less package is a Grunt plugin that compiles LESS files to CSS. It provides a variety of options to customize the compilation process, such as specifying source maps, compressing the output, and including additional paths for @import directives.
Basic Compilation
This feature allows you to compile LESS files into CSS. The 'paths' option specifies directories to scan for @import directives.
{
"less": {
"development": {
"options": {
"paths": ["assets/css"]
},
"files": {
"path/to/result.css": "path/to/source.less"
}
}
}
}Source Maps
This feature enables the generation of source maps, which help in debugging by mapping the compiled CSS back to the original LESS source.
{
"less": {
"development": {
"options": {
"sourceMap": true,
"sourceMapFilename": "path/to/result.css.map",
"sourceMapURL": "result.css.map"
},
"files": {
"path/to/result.css": "path/to/source.less"
}
}
}
}Compression
This feature allows you to compress the output CSS, reducing file size for production environments.
{
"less": {
"production": {
"options": {
"compress": true
},
"files": {
"path/to/result.min.css": "path/to/source.less"
}
}
}
}Custom Functions
This feature allows you to define custom functions that can be used within your LESS files.
{
"less": {
"development": {
"options": {
"functions": {
"add": function(less, a, b) {
return a + b;
}
}
},
"files": {
"path/to/result.css": "path/to/source.less"
}
}
}
}The 'less' package is the official LESS compiler. It can be used directly via the command line or integrated into build systems. It offers similar functionalities to grunt-contrib-less but does not provide the Grunt-specific integration.
The 'gulp-less' package is a Gulp plugin for compiling LESS files. It offers similar functionalities to grunt-contrib-less but is designed to work within the Gulp task runner ecosystem.
The 'less-loader' package is a Webpack loader for compiling LESS files. It integrates LESS compilation into the Webpack build process, offering similar functionalities but within the Webpack ecosystem.
Compile LESS files to CSS
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 grunt-contrib-less --save-dev
Once the plugin has been installed, it may be enabled inside your Gruntfile with this line of JavaScript:
grunt.loadNpmTasks('grunt-contrib-less');
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.
Run this task with the grunt less command.
Task targets, files and options may be specified according to the grunt Configuring tasks guide.
Type: String Array Function
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.
If you specify a function the source filepath will be the first argument. You can return either a string or an array of paths to be used.
Type: String
Default: ""
A path to add on to the start of every URL resource.
Type: Boolean
Default: false
Compress output by removing some whitespaces.
Type: Array
Default: null
Allows passing plugins
Type: Boolean
Default: true
Enforce the CSS output is compatible with Internet Explorer 8.
For example, the data-uri function encodes a file in base64 encoding and embeds it into the generated CSS files as a data-URI. Because Internet Explorer 8 limits data-uris to 32KB, the ieCompat option prevents less from exceeding this.
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: Boolean
Default: false
When enabled, math is required to be in parenthesis.
Type: Boolean
Default: false
When enabled, less will validate the units used (e.g. 4px/2px = 2, not 2px and 4em/2px throws an error).
Type: Boolean
Default: false
Read @import'ed files synchronously from disk.
Type: String
Default: false
Configures -sass-debug-info support.
Accepts following values: comments, mediaquery, all.
Type: Boolean
Default: false
Rewrite URLs to be relative. false: do not modify URLs.
Type: Object
Default: none
Define custom functions to be available within your LESS stylesheets. The function's name must be lowercase. In the definition, the first argument is the less object, and subsequent arguments are from the less function call. Values passed to the function are types defined within less, the return value may be either one of them or primitive. See the LESS documentation for more information on the available types.
Type: Boolean
Default: false
Enable source maps.
Type: String
Default: none
Write the source map to a separate file with the given filename.
Type: String
Default: none
Override the default URL that points to the source map from the compiled CSS file.
Type: String
Default: none
Sets the base path for the less file paths in the source map.
Type: String
Default: none
Adds this path onto the less file paths in the source map.
Type: Boolean
Default: false
Puts the map (and any less files) as a base64 data uri into the output css file.
Type: Boolean
Default: false
Puts the less files into the map instead of referencing them.
Type: Object
Default: none
Overrides global variables. Equivalent to --modify-vars='VAR=VALUE' option in less.
Type: String
Default: none
less: {
development: {
options: {
paths: ["assets/css"]
},
files: {
"path/to/result.css": "path/to/source.less"
}
},
production: {
options: {
paths: ["assets/css"],
plugins: [
new (require('less-plugin-autoprefix'))({browsers: ["last 2 versions"]}),
new (require('less-plugin-clean-css'))(cleanCssOptions)
],
modifyVars: {
imgPath: '"http://mycdn.com/path/to/images"',
bgColor: 'red'
}
},
files: {
"path/to/result.css": "path/to/source.less"
}
}
}
modifyVars to work when less file ends with a comment.Task submitted by Tyler Kellen
This file was generated on Mon Feb 01 2016 10:55:38.
FAQs
Compile LESS files to CSS
We found that grunt-contrib-less demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 7 open source maintainers collaborating on the project.
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