Introduction to CSS Custom Properties

High-level programming language.

CSS Custom Properties, often referred to as CSS Variables, are a powerful tool that allows you to enhance your CSS code, making it more dynamic and reusable. This article will provide an introduction to CSS Custom Properties, highlighting their differences from preprocessor variables, and explaining their syntax and declaration.

Understanding CSS Custom Properties

CSS Custom Properties are entities defined by CSS authors that contain specific values to be reused throughout a document. They are set using custom property notation, i.e., --name: value;. They are case-sensitive, unlike other CSS properties, and can be declared within any rule set.

The power of CSS Custom Properties lies in their potential to be updated in real-time through JavaScript, which is not possible with preprocessor variables. This allows for dynamic changes in your stylesheets, such as theme switching or responsive design based on user interaction.

Differences Between CSS Custom Properties and Preprocessor Variables

While both CSS Custom Properties and preprocessor variables (like those in Sass or Less) allow for reusable values, there are key differences:

• Scope: Preprocessor variables are limited in scope to the file or block of code where they are declared. In contrast, CSS Custom Properties follow the rules of CSS cascading and inheritance, making them available throughout the entire DOM tree.

• JavaScript Interaction: Preprocessor variables cannot be manipulated with JavaScript as they are compiled into regular CSS before reaching the browser. CSS Custom Properties, however, can be updated in real-time using JavaScript, allowing for dynamic styling.

• Browser Handling: Preprocessor variables are handled at compile-time, while CSS Custom Properties are handled by the browser at runtime. This means that CSS Custom Properties can be used and updated in the live environment.

Syntax and Declaration of CSS Custom Properties

Declaring a CSS Custom Property is straightforward. They are declared within a selector and use a double hyphen prefix --. Here's an example:

:root {
  --main-color: #06c;
}

In this example, --main-color is the custom property, and #06c is its value. The :root selector is often used for global custom properties, but they can be declared within any selector.

To use a custom property, you use the var() function:

body {
  background-color: var(--main-color);
}

In this case, the background color of the body will be the color defined in --main-color.

In conclusion, CSS Custom Properties offer a powerful way to create dynamic, reusable values in your CSS. Understanding their differences from preprocessor variables and mastering their syntax and declaration is the first step towards leveraging their full potential.