Using CSS Variables (Custom Properties) – in CSS
Welcome to this comprehensive, student-friendly guide on CSS Variables, also known as Custom Properties! 🎨 Whether you’re just starting out or looking to deepen your understanding, this tutorial will walk you through everything you need to know. By the end, you’ll be using CSS Variables like a pro, making your stylesheets more efficient and easier to maintain. Let’s dive in!
What You’ll Learn 📚
- What CSS Variables are and why they’re useful
- How to declare and use CSS Variables
- Practical examples from simple to complex
- Common questions and troubleshooting tips
Introduction to CSS Variables
CSS Variables, or Custom Properties, are a way to store values that you can reuse throughout your CSS. Think of them like variables in programming languages. They help you keep your code DRY (Don’t Repeat Yourself) and make it easier to manage and update styles.
Key Terminology
- CSS Variable: A reusable value defined in CSS, prefixed with
--. - Custom Property: Another term for CSS Variable.
- DRY: An acronym for “Don’t Repeat Yourself,” a principle aimed at reducing repetition in code.
Simple Example: Declaring and Using CSS Variables
:root { /* Declare a CSS Variable */ --primary-color: #3498db;}body { /* Use the CSS Variable */ background-color: var(--primary-color);}In this example, we declare a CSS Variable called --primary-color and assign it a value of #3498db. We then use this variable in the background-color property of the body element.
Progressively Complex Examples
Example 1: Changing Themes
:root { --primary-color: #3498db; --secondary-color: #2ecc71;}.theme-light { --primary-color: #ecf0f1; --secondary-color: #bdc3c7;}body { background-color: var(--primary-color); color: var(--secondary-color);}Here, we define a light theme by overriding the default variables. This allows for easy theme switching by simply changing the class on the body element.
Example 2: Responsive Design
:root { --base-font-size: 16px;}@media (min-width: 768px) { :root { --base-font-size: 18px; }}body { font-size: var(--base-font-size);}This example demonstrates how to adjust font sizes responsively using CSS Variables. The --base-font-size changes based on the screen width.
Example 3: Dynamic Updates with JavaScript
<button id="changeColor">Change Color</button>:root { --button-color: #3498db;}button { background-color: var(--button-color);}document.getElementById('changeColor').addEventListener('click', function() { document.documentElement.style.setProperty('--button-color', '#e74c3c');});In this interactive example, clicking the button changes its color using JavaScript to update the CSS Variable.
Common Questions and Answers
- What are CSS Variables used for?
CSS Variables allow you to reuse values throughout your stylesheet, making it easier to maintain and update your code.
- Can CSS Variables be used in all browsers?
Most modern browsers support CSS Variables, but it’s always good to check compatibility if you’re supporting older browsers.
- How do I declare a CSS Variable?
Declare a CSS Variable within a selector using the
--variable-name: value;syntax. - How do I use a CSS Variable?
Use the
var(--variable-name)function to apply the variable’s value. - Can CSS Variables be updated dynamically?
Yes, you can update CSS Variables dynamically using JavaScript.
Troubleshooting Common Issues
Ensure your variable names are prefixed with
--and used withvar().
If a variable isn’t working, check for typos in the variable name or ensure it’s declared in a scope accessible to where it’s used.
Practice Exercises
Try creating a dark theme using CSS Variables or make a responsive layout with different font sizes!
For more information, check out the MDN Web Docs on CSS Custom Properties.