mirror of
https://github.com/adambard/learnxinyminutes-docs.git
synced 2024-11-27 13:32:56 +03:00
390 lines
7.2 KiB
Markdown
390 lines
7.2 KiB
Markdown
---
|
|
language: less
|
|
filename: learnless.less
|
|
contributors:
|
|
- ["Saravanan Ganesh", "http://srrvnn.me"]
|
|
---
|
|
|
|
Less is a CSS pre-processor, that adds features such as variables, nesting, mixins and more.
|
|
Less (and other preprocessors, such as [Sass](http://sass-lang.com/)) help developers to write maintainable and DRY (Don't Repeat Yourself) code.
|
|
|
|
```css
|
|
|
|
|
|
//Single line comments are removed when Less is compiled to CSS.
|
|
|
|
/*Multi line comments are preserved. */
|
|
|
|
|
|
|
|
/* Variables
|
|
==============================*/
|
|
|
|
|
|
/* You can store a CSS value (such as a color) in a variable.
|
|
Use the '@' symbol to create a variable. */
|
|
|
|
@primary-color: #a3a4ff;
|
|
@secondary-color: #51527f;
|
|
@body-font: 'Roboto', sans-serif;
|
|
|
|
/* You can use the variables throughout your stylesheet.
|
|
Now if you want to change a color, you only have to make the change once.*/
|
|
|
|
body {
|
|
background-color: @primary-color;
|
|
color: @secondary-color;
|
|
font-family: @body-font;
|
|
}
|
|
|
|
/* This would compile to: */
|
|
|
|
body {
|
|
background-color: #a3a4ff;
|
|
color: #51527F;
|
|
font-family: 'Roboto', sans-serif;
|
|
}
|
|
|
|
|
|
/* This is much more maintainable than having to change the color
|
|
each time it appears throughout your stylesheet. */
|
|
|
|
|
|
|
|
/* Mixins
|
|
==============================*/
|
|
|
|
|
|
/* If you find you are writing the same code for more than one
|
|
element, you might want to reuse that easily.*/
|
|
|
|
.center {
|
|
display: block;
|
|
margin-left: auto;
|
|
margin-right: auto;
|
|
left: 0;
|
|
right: 0;
|
|
}
|
|
|
|
/* You can use the mixin by simply adding the selector as a style */
|
|
|
|
div {
|
|
.center;
|
|
background-color: @primary-color;
|
|
}
|
|
|
|
/* Which would compile to: */
|
|
|
|
.center {
|
|
display: block;
|
|
margin-left: auto;
|
|
margin-right: auto;
|
|
left: 0;
|
|
right: 0;
|
|
}
|
|
div {
|
|
display: block;
|
|
margin-left: auto;
|
|
margin-right: auto;
|
|
left: 0;
|
|
right: 0;
|
|
background-color: #a3a4ff;
|
|
}
|
|
|
|
/* You can omit the mixin code from being compiled by adding parenthesis
|
|
after the selector */
|
|
|
|
.center() {
|
|
display: block;
|
|
margin-left: auto;
|
|
margin-right: auto;
|
|
left: 0;
|
|
right: 0;
|
|
}
|
|
|
|
div {
|
|
.center;
|
|
background-color: @primary-color;
|
|
}
|
|
|
|
/* Which would compile to: */
|
|
div {
|
|
display: block;
|
|
margin-left: auto;
|
|
margin-right: auto;
|
|
left: 0;
|
|
right: 0;
|
|
background-color: #a3a4ff;
|
|
}
|
|
|
|
|
|
|
|
/* Nesting
|
|
==============================*/
|
|
|
|
|
|
/* Less allows you to nest selectors within selectors */
|
|
|
|
ul {
|
|
list-style-type: none;
|
|
margin-top: 2em;
|
|
|
|
li {
|
|
background-color: #f00;
|
|
}
|
|
}
|
|
|
|
/* '&' will be replaced by the parent selector. */
|
|
/* You can also nest pseudo-classes. */
|
|
/* Keep in mind that over-nesting will make your code less maintainable.
|
|
Best practices recommend going no more than 3 levels deep when nesting.
|
|
For example: */
|
|
|
|
ul {
|
|
list-style-type: none;
|
|
margin-top: 2em;
|
|
|
|
li {
|
|
background-color: red;
|
|
|
|
&:hover {
|
|
background-color: blue;
|
|
}
|
|
|
|
a {
|
|
color: white;
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Compiles to: */
|
|
|
|
ul {
|
|
list-style-type: none;
|
|
margin-top: 2em;
|
|
}
|
|
|
|
ul li {
|
|
background-color: red;
|
|
}
|
|
|
|
ul li:hover {
|
|
background-color: blue;
|
|
}
|
|
|
|
ul li a {
|
|
color: white;
|
|
}
|
|
|
|
|
|
|
|
/* Functions
|
|
==============================*/
|
|
|
|
|
|
/* Less provides functions that can be used to accomplish a variety of
|
|
tasks. Consider the following: */
|
|
|
|
/* Functions can be invoked by using their name and passing in the
|
|
required arguments. */
|
|
|
|
body {
|
|
width: round(10.25px);
|
|
}
|
|
|
|
.header {
|
|
background-color: lighten(#000, 0.5);
|
|
}
|
|
|
|
.footer {
|
|
background-color: fadeout(#000, 0.25)
|
|
}
|
|
|
|
/* Compiles to: */
|
|
|
|
body {
|
|
width: 10px;
|
|
}
|
|
|
|
.header {
|
|
background-color: #010101;
|
|
}
|
|
|
|
.footer {
|
|
background-color: rgba(0, 0, 0, 0.75);
|
|
}
|
|
|
|
/* You may also define your own functions. Functions are very similar to
|
|
mixins. When trying to choose between a function or a mixin, remember
|
|
that mixins are best for generating CSS while functions are better for
|
|
logic that might be used throughout your Less code. The examples in
|
|
the 'Math Operators' section are ideal candidates for becoming a reusable
|
|
function. */
|
|
|
|
/* This function calculates the average of two numbers: */
|
|
|
|
.average(@x, @y) {
|
|
@average-result: ((@x + @y) / 2);
|
|
}
|
|
|
|
div {
|
|
.average(16px, 50px); // "call" the mixin
|
|
padding: @average-result; // use its "return" value
|
|
}
|
|
|
|
/* Compiles to: */
|
|
|
|
div {
|
|
padding: 33px;
|
|
}
|
|
|
|
|
|
|
|
/*Extend (Inheritance)
|
|
==============================*/
|
|
|
|
|
|
/*Extend is a way to share the properties of one selector with another. */
|
|
|
|
.display {
|
|
height: 50px;
|
|
}
|
|
|
|
.display-success {
|
|
&:extend(.display);
|
|
border-color: #22df56;
|
|
}
|
|
|
|
/* Compiles to: */
|
|
.display,
|
|
.display-success {
|
|
height: 50px;
|
|
}
|
|
.display-success {
|
|
border-color: #22df56;
|
|
}
|
|
|
|
/* Extending a CSS statement is preferable to creating a mixin
|
|
because of the way it groups together the classes that all share
|
|
the same base styling. If this was done with a mixin, the properties
|
|
would be duplicated for each statement that
|
|
called the mixin. While it won't affect your workflow, it will
|
|
add unnecessary bloat to the files created by the Less compiler. */
|
|
|
|
|
|
|
|
/*Partials and Imports
|
|
==============================*/
|
|
|
|
|
|
/* Less allows you to create partial files. This can help keep your Less
|
|
code modularized. Partial files conventionally begin with an '_',
|
|
e.g. _reset.less. and are imported into a main less file that gets
|
|
compiled into CSS */
|
|
|
|
/* Consider the following CSS which we'll put in a file called _reset.less */
|
|
|
|
html,
|
|
body,
|
|
ul,
|
|
ol {
|
|
margin: 0;
|
|
padding: 0;
|
|
}
|
|
|
|
/* Less offers @import which can be used to import partials into a file.
|
|
This differs from the traditional CSS @import statement which makes
|
|
another HTTP request to fetch the imported file. Less takes the
|
|
imported file and combines it with the compiled code. */
|
|
|
|
@import 'reset';
|
|
|
|
body {
|
|
font-size: 16px;
|
|
font-family: Helvetica, Arial, Sans-serif;
|
|
}
|
|
|
|
/* Compiles to: */
|
|
|
|
html, body, ul, ol {
|
|
margin: 0;
|
|
padding: 0;
|
|
}
|
|
|
|
body {
|
|
font-size: 16px;
|
|
font-family: Helvetica, Arial, Sans-serif;
|
|
}
|
|
|
|
|
|
|
|
/* Math Operations
|
|
==============================*/
|
|
|
|
|
|
/* Less provides the following operators: +, -, *, /, and %. These can
|
|
be useful for calculating values directly in your Less files instead
|
|
of using values that you've already calculated by hand. Below is an example
|
|
of a setting up a simple two column design. */
|
|
|
|
@content-area: 960px;
|
|
@main-content: 600px;
|
|
@sidebar-content: 300px;
|
|
|
|
@main-size: @main-content / @content-area * 100%;
|
|
@sidebar-size: @sidebar-content / @content-area * 100%;
|
|
@gutter: 100% - (@main-size + @sidebar-size);
|
|
|
|
body {
|
|
width: 100%;
|
|
}
|
|
|
|
.main-content {
|
|
width: @main-size;
|
|
}
|
|
|
|
.sidebar {
|
|
width: @sidebar-size;
|
|
}
|
|
|
|
.gutter {
|
|
width: @gutter;
|
|
}
|
|
|
|
/* Compiles to: */
|
|
|
|
body {
|
|
width: 100%;
|
|
}
|
|
|
|
.main-content {
|
|
width: 62.5%;
|
|
}
|
|
|
|
.sidebar {
|
|
width: 31.25%;
|
|
}
|
|
|
|
.gutter {
|
|
width: 6.25%;
|
|
}
|
|
|
|
|
|
```
|
|
|
|
## Practice Less
|
|
|
|
If you want to play with Less in your browser, check out:
|
|
* [Codepen](http://codepen.io/)
|
|
* [LESS2CSS](http://lesscss.org/less-preview/)
|
|
|
|
## Compatibility
|
|
|
|
Less can be used in any project as long as you have a program to compile it into CSS. You'll want to verify that the CSS you're using is compatible with your target browsers.
|
|
|
|
[QuirksMode CSS](http://www.quirksmode.org/css/) and [CanIUse](http://caniuse.com) are great resources for checking compatibility.
|
|
|
|
## Further reading
|
|
* [Official Documentation](http://lesscss.org/features/)
|
|
* [Less CSS - Beginner's Guide](http://www.hongkiat.com/blog/less-basic/)
|