Jump to content

Less (style sheet language)

From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by 84.52.88.87 (talk) at 13:48, 3 August 2018. The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Less
Designed byAlexis Sellier
DeveloperAlexis Sellier, Dmitry Fadeyev
First appeared2009; 15 years ago (2009)
Stable release
3.7.1[1] / July 11, 2018; 6 years ago (2018-07-11)
Typing disciplinedynamic
Implementation languageJavaScript
OSCross-platform
LicenseApache License 2
Filename extensions.less
Websitelesscss.org
Influenced by
CSS, Sass
Influenced
Sass, Less Framework, Bootstrap

Less (Leaner Style Sheets; sometimes stylized as LESS) is a dynamic preprocessor style sheet language that can be compiled into Cascading Style Sheets (CSS) and run on the client side or server side.[2] Designed by Alexis Sellier, Less is influenced by Sass and has influenced the newer "SCSS" syntax of Sass, which adapted its CSS-like block formatting syntax.[3] Less is open source. Its first version was written in Ruby; however, in the later versions, use of Ruby has been deprecated and replaced by JavaScript. The indented syntax of Less is a nested metalanguage, as valid CSS is valid Less code with the same semantics. Less provides the following mechanisms: variables, nesting, mixins, operators and functions; the main difference between Less and other CSS precompilers being that Less allows real-time compilation via less.js by the browser.[2][4]

Variables

Less allows variables to be defined. Variables in Less are defined with an at sign (@). Variable assignment is done with a colon (:).

During translation, the values of the variables are inserted into the output CSS document.[2] 

@pale-green-color: #4D926F;

#header {
  color: @pale-green-color;
}
h2 {
  color: @pale-green-color;
}

The code above in Less would compile to the following CSS code. 

#header {
  color: #4D926F;
}
h2 {
  color: #4D926F;
}

Mixins

Mixins allow embedding all the properties of a class into another class by including the class name as one of its properties, thus behaving as a sort of constant or variable. They can also behave like functions, and take arguments. CSS does not support Mixins: Any repeated code must be repeated in each location. Mixins allow for more efficient and clean code repetitions, as well as easier alteration of code.[2] 

.rounded-corners (@radius: 5px 10px 8px 2px) {
  -webkit-border-radius: @radius;
  -moz-border-radius: @radius;
  border-radius: @radius;
}

#header {
  .rounded-corners;
}
#footer {
  .rounded-corners(10px 25px 35px 0px);
}

The above code in Less would compile to the following CSS code: 

#header {
  -webkit-border-radius: 5px 10px 8px 2px;
  -moz-border-radius: 5px 10px 8px 2px;
  border-radius: 5px 10px 8px 2px;
}
#footer {
  -webkit-border-radius: 10px 25px 35px 0px;
  -moz-border-radius: 10px 25px 35px 0px;
  border-radius: 10px 25px 35px 0px;
}

Less has a special type of ruleset called parametric mixins which can be mixed in like classes, but accepts parameters. 

#header {
  h1 {
    font-size: 26px;
    font-weight: bold;
  }
  p {
    font-size: 16px;
    a {
      text-decoration: none;
      color: red;
      &:hover {
        border-width: 1px;
        color: #fff;
      }
    }
  }
}

The above code in Less would compile to the following CSS code: 

#header h1 {
  font-size: 26px;
  font-weight: bold;
}
#header p {
  font-size: 16px;
}
#header p a {
  text-decoration: none;
  color: red;
}
#header p a:hover {
  border-width: 1px;
  color: #fff;
}

Functions and operations

Less allows operations and functions. Operations allow addition, subtraction, division and multiplication of property values and colors, which can be used to create complex relationships between properties. Functions map one-to-one with JavaScript code, allowing manipulation of values. 

@the-border: 1px;
@base-color: #111;
@red:        #842210;

#header {
  color: @base-color * 3;
  border-left: @the-border;
  border-right: @the-border * 3;
}
#footer {
  color: @base-color + #003300;
  border-color: desaturate(@red, 10%);
}

The above code in Less would compile to the following CSS code: 

#header {
  color: #333333;
  border-left: 1px;
  border-right: 3px;
}
#footer {
  color: #114411;
  border-color: #7d2717;
}

Comparison

Sass

Both Sass and Less are CSS preprocessors, which allow writing clean CSS in a programming construct instead of static rules.[5]

Less is inspired by Sass.[6][3] Sass was designed to both simplify and extend CSS, so things like curly braces were removed from the syntax. Less was designed to be as close to CSS as possible, and as a result existing CSS can be used as valid Less code.[7]

The newer versions of Sass also introduced a CSS-like syntax called SCSS (Sassy CSS).

Use on sites

Less can be applied to sites in a number of ways. One option is to include the less.js JavaScript file to convert the code on-the-fly. The browser then renders the output CSS. Another option is to render the Less code into pure CSS and upload the CSS to a site. With this option no .less files are uploaded and the site does not need the less.js JavaScript converter.

Less software

Name Description Software License Platform Functionality
WinLess GUI Less Compiler Apache 2.0[8] Windows Compiler
Crunch Less editor and compiler (requires Adobe AIR) GPL[9] Windows, Mac OS X Compiler
Editor
less.js-windows Simple command-line utility for Windows that will compile *.less files to CSS using less.js. MIT License[10] Windows Compiler
less.app Less Compiler Proprietary Mac OS X Compiler
CodeKit Less Compiler Proprietary Mac OS X Compiler
LessEngine Less Compiler Free OpenCart Plugin Compiler
SimpLESS Less Compiler free but no explicit license[11] Windows
Mac OS X
Linux		 Compiler
Chirpy Less Compiler Ms-PL[12] Visual Studio Plugin Compiler
Mindscape Web Workbench Syntax highlighting and IntelliSense for Less and Sass Proprietary Visual Studio Plugin Compiler
Syntax Highlighting
Eclipse Plugin for Less Eclipse Plugin EPL 1.0[13] Eclipse Plugin Syntax highlighting
Content assist
Compiler
mod_less Apache2 module to compile Less on the fly Open Source Linux Compiler
grunt-contrib-less Node.js Grunt task to convert Less to CSS Open Source Node.js Compiler
Web Essentials Visual Studio extension with support for Less and Sass Apache 2.0 Windows Syntax highlighting, Content assist, Compiler
clessc Pure C++ compiler GPL at least Windows, Linux, MacOS Compiler

See also

References

  1. ^ "CHANGELOG". GitHub.
  2. ^ a b c d Official Less website Official Less website
  3. ^ a b Sass and Less Archived 2009-06-21 at the Wayback Machine Sass and Less
  4. ^ "css - Is there a SASS.js? Something like LESS.js?". Stack Overflow.
  5. ^ What's Wrong With CSS What's Wrong With CSS
  6. ^ About Less About
  7. ^ Sass/Less Comparison
  8. ^ [1] WinLess github Issue "License Information"
  9. ^ Crunch's LICENSE.txt at github Crunch's LICENSE.txt at github
  10. ^ [2] github license
  11. ^ [3] license file at github (placeholder)
  12. ^ [4] Chirpy License Information at CodePlex
  13. ^ Eclipse Plugin for Less homepage Eclipse Plugin for Less homepage
Retrieved from "https://en.wikipedia.org/w/index.php?title=Less_(style_sheet_language)&oldid=853259904"