LESS is a Leaner Style Sheets, a simple CSS pre-processor that facilitates the creation of manageable, customizable, and reusable style sheets for websites. It is a dynamic style sheet language that enhances the working power of CSS. LESS supports cross-browser compatibility. CSS pre-processor is a scripting language that improves CSS and gets compiled into regular CSS syntax so that the web browser can use it. It is also a backward-compatible language extension for CSS that provides functionalities like variables, functions, mixins, and operations that enable us to build dynamic CSS.
Mixins in less: Mixins in LESS, along with understanding their implementation & usage through the example. A CSS preprocessor is a program that generates the CSS code by using the defined preprocessor ruleset & facilitates reducing the overall complexity of CSS code. LESS is a CSS preprocessor that is a CSS backward-compatible language extension. Mixins in LESS, are a way to include a bunch of CSS properties from one ruleset to another i.e multiple times in the same file.
Mixin Guards: If you want to match simple values or a number of arguments on expressions, then you can use guards. It is associated with a mixin declaration and includes a condition that is attached to a mixin. Each mixin will have one or more guards which are separated by a comma; a guard must be enclosed within parentheses. LESS uses guarded mixins instead of if/else statements and performs calculations to specify matched mixin.
Different types of mixin guards:
- Guard Comparison Operators
Parameter: You can use the comparison operator (=) to compare numbers, strings, identifiers, etc. There are some comparison operators usable in guards: >, >=, =, =<. Additionally, the keyword true is the only truthy value, making these two mixins equivalent.
- Guard Logical Operators:
Parameter: You can use keywords to work around logical operators with guards.
- Type Checking Functions: It contains the built-in functions to determine the value types for matching mixins.
Mixin guards:
Syntax:
.p-style(@size) when (@size<=50){
font-size: @size;
color:green;
}
Example 1: The following example, demonstrates the use of mixin guards.
HTML
<!doctype html> <head> <title>Mixin Guards</title> <link rel="stylesheet" href="style.css" type="text/css" /> </head> <body><br><br> <h1><b>neveropen</b></h1> <h2>Learning Mixin Guards...</h2> </body> </html> |
style.less: Create a less file.
CSS
.p-style(@size) when (@size<=50){ font-size: @size; color:green; } .p-style(@size) when (@size>50){ font-size: @size; color:blue; } h1{ .p-style(40px); } |
Now, to compile the above LESS code to CSS code, run the following command:
lessc style.less style.css
The compiled CSS file comes to be:
style.css
CSS
h1 { font-size: 40px; color: green; } |
Output:
Example 2: The following example demonstrates the use of mixin guards.
HTML
<!doctype html> <head> <title>Mixin Guards</title> <link rel="stylesheet" href="style.css" type="text/css" /> </head> <body> <h1 class="cont1">neveropen</h1> <h3 class="cont2">Learning Mixin Guards...</h3> </body> </html> |
style.less: Creates the less file
CSS
.One (@primary) when (lightness(@primary) >= 50%) { font-size: 50px; } .One (@primary) when (lightness(@primary) < 50%) { font-size: 40px; } .One (@primary) { color: @primary; } .cont1 { text-align: center; .One(green) } .cont2 { text-align: center; .One(black) } |
Now, to compile the above LESS code to CSS code, run the following command:
lessc style.less style.css
The compiled CSS file comes to be:
style.css
CSS
.cont1 { text-align: center; font-size: 40px; color: green; } .cont2 { text-align: center; font-size: 40px; color: black; } |
Output:
Reference: https://lesscss.org/features/#mixins-feature-mixin-guards-feature
