CSS Variables
CSS Variables, also known as CSS Custom Properties, are a powerful feature introduced in CSS3 that allow you to define reusable values that can be used throughout your CSS code. These variables are defined at the root level of your CSS, and their values can be changed dynamically using JavaScript, making it easier to create consistent and maintainable styles across your web project.
The syntax for defining a CSS variable is as follows:
/* Define a CSS variable */
:root {
--variable-name: value;
}:root: Represents the root element, which is the top-level element in the document (usually the<html>element). CSS variables should be defined inside the:rootselector to make them globally accessible within the entire CSS document.--variable-name: This is the name of the variable. It starts with two dashes (--) followed by the variable name.value: The value assigned to the variable. It can be any valid CSS value, such as colors, dimensions, font names, etc.
Example:
/* Define CSS variables */
:root {
--primary-color: #007bff;
--font-size: 16px;
}
/* Use the CSS variables */
body {
color: var(--primary-color);
font-size: var(--font-size);
}In this example, we define two CSS variables --primary-color and --font-size with their respective values. Then, we use these variables in the body selector to set the text color and font size.
CSS variables can also be inherited by child elements:
.container {
--text-color: red;
}
.header {
color: var(--text-color); /* Inherits the value from .container */
}One of the main advantages of using CSS variables is their ability to change their values dynamically using JavaScript, making it easy to switch themes, update colors, or adapt styles based on user interactions or system preferences.
// JavaScript to change the CSS variable value dynamically
document.documentElement.style.setProperty('--primary-color', 'green');Using CSS variables promotes modularity, reusability, and maintainability in your CSS codebase. It helps keep your styles consistent and allows for easy global changes without the need to search and replace values throughout your entire CSS code. However, note that CSS variables are supported in modern browsers and may require fallback values or alternative approaches for older browsers. Always check for browser compatibility before relying heavily on CSS variables.