Working with CSS Variables

CSS variables, also known as custom properties, are a powerful tool for simplifying and streamlining your CSS. They allow you to store values that can be reused throughout your stylesheet, making it easier to maintain and update your styles. In this chapter, we will cover how to use CSS variables and the benefits they provide.

Defining CSS Variables

CSS variables are defined using the -- prefix, followed by the variable name. The value of the variable is assigned using the : symbol. CSS variables can be defined anywhere in your stylesheet, but it is generally best practice to define them at the top of your stylesheet or in a separate file.

For example, to define a variable for the primary color of your website, you could use the following CSS:

:root {
  --primary-color: #0074D9;
}

This will create a variable called --primary-color with a value of #0074D9, which is a blue color.

Using CSS Variables

To use a CSS variable, you simply reference it using the var() function. The var() function takes the variable name as its first argument, and an optional fallback value as the second argument.

For example, to use the --primary-color variable defined above as the color for all a elements, you could use the following CSS:

a {
  color: var(--primary-color);
}

This will set the color of all a elements to the value of the --primary-color variable. If the --primary-color variable is not defined, the fallback value of #0074D9 will be used.

Benefits of Using CSS Variables

There are several benefits to using CSS variables:

• Simplify and streamline your CSS: CSS variables allow you to store values that can be reused throughout your stylesheet, reducing the need for repetitive and redundant code.
• Make updating your styles easier: By storing values in variables, you can easily update your styles by changing the value of the variable. This is especially useful for global values, such as colors or font sizes.
• Improve maintainability: CSS variables make it easier to maintain and update your styles, as you only need to change the value of the variable rather than searching for and updating the value throughout your stylesheet.

Tips for Using CSS Variables

• Define CSS variables at the top of your stylesheet or in a separate file for easy reference.
• Use descriptive and intuitive names for your variables to improve readability and maintainability.
• Use the var() function to reference CSS variables in your styles.
• Use fallback values in the var() function to ensure that your styles are consistent if a variable is not defined.

Conclusion

CSS variables are a powerful tool for simplifying and streamlining your CSS. By defining and using variables, you can improve the maintainability and updateability of your styles. By following best practices and using descriptive and intuitive variable names, you can take full advantage of the benefits that CSS variables provide.

Exercises

To review these concepts, we will go through a series of exercises designed to test your understanding and apply what you have learned.

:root {
  --main-font-size: 16px;
}

h1 {
  font-size: 1.5em;
}

:root {
  --secondary-color: #FF851B;
}

button {
  background-color: var(--secondary-color);
}

:root {
  --border-radius: 5px;
}

input {
  border-radius: var(--border-radius);
}

:root {
  --box-shadow: 0 5px 10px rgba(0, 0, 0, 0.2);
}

div {
  box-shadow: var(--box-shadow);
}

:root {
  --main-font-family: Arial, sans-serif;
}

p {
  font-family: var(--main-font-family);
}