CSS Variables, also known as CSS Custom Properties, were introduced in CSS3. With CSS Variables, you can define a variable and reuse it throughout your CSS. This can save a lot of time and make your code more maintainable.
CSS Variables can be used to store values such as colors, font sizes, and spacing. You can even use them to generate dynamic themes for your website. By changing the value of a single CSS Variable, you can update the colors and styles throughout your site.
Overall, CSS Variables are a powerful tool for web developers to improve the readability, maintainability, and flexibility of their code.
getComputedStyle() method. This method returns a
CSSStyleDeclaration object that contains all the CSS rules applied to an element, including any variables defined using the
To access a variable, you need to use the
getPropertyValue() method of the
CSSStyleDeclaration object. This method takes the name of the variable as its argument and returns its value, as a string.
You can also set the value of a variable using the
setProperty() method of the
CSSStyleDeclaration object. This method takes the name of the property and its new value as arguments.
// Change the value of a CSS variable const root = document.documentElement; root.style.setProperty('--primary-color', '#ff0000');
setProperty method of the
style property on an element to set the value of a CSS variable.
const element = document.querySelector('element-selector'); element.style.setProperty('--variable-name', 'new-value');
In this code,
element-selector is the selector for the element you want to modify, and
--variable-name is the name of the CSS variable you want to modify. You can set
new-value to any valid CSS value.
1. Define Variables in a Central Location
To keep your code organized and maintainable, define your CSS variables in a central location like a separate CSS file. This will make it easy to update the values of your variables if needed and ensure consistency across your web pages.
2. Use Descriptive Variable Names
Use descriptive variable names that make it easy to understand what the variable is used for. This will help you identify the purpose of the variable when reading the code and prevent confusion when making changes.
3. Avoid Overusing Variables
While CSS variables can be powerful tools, avoid overusing them. Use variables only for properties that are likely to change frequently. If a property is static, hard code it instead of creating a variable for it. This will ensure that your code remains easy to maintain and understand.
4. Use Default Values
Provide default values for your variables in case they are not defined or supported. This will prevent unexpected behavior in older browsers and ensure that your web pages remain functional.
5. Access Variables Using getComputedStyle
One approach is to use the
document.styleSheets property to access the CSS rules of a stylesheet, and then iterate through them to find the rule that contains the variable you want to read. Once you find the rule, you can extract the value of the variable from its
Another approach is to use the
match() method of a CSS rule’s
cssText property to find the variable you want to read. This method extracts a string that represents the entire CSS rule, and you can then use regular expressions to find the variable and its value.
Both of these alternative methods have their pros and cons, so it is important to choose the approach that works best for your specific project.
CSS variables, also known as CSS custom properties, allow developers to declare reusable values in CSS. These variables can then be used throughout the CSS document, making it easier to maintain and update styles across a website.
- Interactive Animations: CSS variables can be used to create interactive animations that respond to user input or changes in the DOM. For example, hovering over an element could trigger a change in the color or scale of the element using CSS variables.
- Easy Customization: CSS variables make it easy for users to customize their experience. For example, a user could change the accent color of a website by adjusting the value of a CSS variable.
- Dynamic Gradients: CSS variables can be used to create dynamic gradients that change based on user input or other factors. For example, the background of a button could change from red to blue when the user clicks it.