LESS and Sass are CSS preprocessors that allow for variables, mixins, and nested rules to make CSS more maintainable. Some key differences are that LESS uses @variables while Sass uses $variables. Both support mixins but LESS calls them with .mixin() while Sass uses @include. Nesting rules in LESS and Sass avoids repetition by nesting selectors within parent elements. Both support math operations and functions to generate CSS values programmatically.

1. LESS & Sass
Overview

2. How to START with

3. Client-side way
Download less.js Create style.less file
http://lesscss.org/ Instead of style.css

4. Link both files with the main HTML doc
<link rel="stylesheet/less" href="styles.less" />
<script src="less.js" ></script>

5. Server-side way
First possibility Second possibility
Download NPM Download Ruby
http://www.ruby-lang.org/en/downloads
https://github.com/isaacs/npm
Or get Node.js For Windows users
http://nodejs.org/ http://rubyinstaller.org
Now start the command prompt

6. If you chose NPM type:
$ npm install -g less

7. If you chose Ruby type:
$ gem install less

8. How to compile the Less code?
Client-side way
It happens automatically when you hit (F5).
You could also use some compilation tools.
Server-side way
$ lessc style.less > style.css
Less compiler Output Css file
Less file

9. LESS Compilers
Remember the client-side way, well this is pretty
much the same, but we have tools to help us.
simpLess CodeKit LiveReload

10. How to START with

11. Just Server-side way (there are dome unofficial client side ways)
$ gem install sass

12. How to compile the Sass code?
Server-side way
$ sass --watch style.scss : style.css
Sass compiler
Watch for compilation
SASS code file CSS code file

13. Less & Sass comparison

14. Variables
just a value container

15. Sometimes we repeat the same value
over and over
#firstElement {
background: #abcdef
}
#secondElement { background: #abcdef
background : #abcdef
}
#thirdElement {
color : #ff91aa;
}
... color : #ff91aa
#nthElement {
color : #ff91aa;
}

16. LESS SASS
@bgColor : #abcdef; $bgColor : #abcdef;
@justColor : #ff91aa; $justColor : #ff91aa;
#firstElement{ #firstElement{
background: @bgColor; background: $bgColor;
} }

17. Mixins
variables on steroids

18. Sometimes we repeat a big chinks of code
with different values over and over
#justElement {
-moz-bordee-radius: 10px;
-webkit-border-radius: 10px;
-o-border-radius: 10px;
border-radius: 10px;
}
#anotherElement {
/* if we want the same*/
}

19. LESS SASS
.roundBorder( @val : 10px ) { @roundBorder( $val : 10x) {
-moz-bordee-radius: @val; -moz-bordee-radius: $val;
-webkit-border-radius: @val; -webkit-border-radius: $val;
-o-border-radius: @val; -o-border-radius: $val;
border-radius: @val; border-radius: $val;
} }
#justElement{ #justElement{
.roundBorder( ); @include roundBorder()
} }
#anatherElement{ #anotherElement{
.roundBorder(17px); @include roundBorder(17px)
} }

20. Nested css code
no more epic repetition code

21. If we have a lot of nested content is tedious to
have address the deepest elements
<div id=“main”> #main {
<p> width:500px
<span>Span text</span> }
<a href=“#”>Link</a> #main p {
</p> width: 150px;
</div> }
#main p span {
color: #abcdef;
}
#main p a {
text-decoration: none;
}

22. LESS and SaSS
#main{
width: 500px; FIRST LEVEL NESTING (P ELEMENT)
p{
width: 150px;
SECOND LEVEL NESTING
Span element
span {
color: #abcdef;
}
a{ SECOND LEVEL NESTING
anchor element
text-decoration: none;
}
}
}

23. Functions & Operations
a way to do the math

24. Operations
LESS example Sass example
// width variable // width variable
@width: 500px; $width : 500px;
#divNewWidth { #divNewWidth {
width: (@width + 10) width: ($width + 10);
} }
Both Sass and Less supports math operators(+|-|*|/|%).

25. Functions
Both Sass and Less supports a variety of Math
and Color functions, that generated specific css
values
Sass functions:
http://sasslang.com/docs/yardoc/Sass/Script/Functions.html
Less functions:
http://lesscss.org/#-color-functions