CSS Counters: A Step-by-Step Tutorial with Examples
Jun 12, 2025 am 10:31 AM
CSS Counters is a tool for creating automatic numbers. 1. Basic usage: define and operate counters through counter-reset and counter-increment, such as "Section X." before h2. 2. Advanced usage: Use nested counters to create complex numbers, such as chapter and subsection numbers. 3. Notes: Ensure the counter is reset correctly, optimize performance, and simplify counter logic. 4. Best practice: Clearly named, define counters in CSS, and use counter-increment and counter-reset reasonably.
CSS Counters is a powerful and flexible tool that helps us create automatically numbered lists, chapters, page numbers and more. Today we will discuss the usage methods and techniques of CSS Counters in depth.
CSS Counters allows us to define and manipulate counters in CSS, which is very useful for generating ordered lists, directories, chapter numbers, and more. By using CSS Counters, we can easily implement some complex typography without relying on JavaScript or other scripting languages.
Let's start with a simple example to illustrate the basic usage of CSS Counters:
body {
counter-reset: section;
}
h2::before {
counter-increment: section;
content: "Section " counter(section) ". ";
} This code defines a counter named section and adds a number before each h2 element. Each time an h2 element is encountered, the value of the counter will increase and "Section X." will be displayed before the h2 element, where X is the current counter value.
Now, let's take a look at some of the advanced usages and tips of CSS Counters.
First, we can use nested counters to create a more complex numbering system. For example, if we want to create numbers for chapters and subsections in an article, we can do this:
body {
counter-reset: chapter section;
}
h1 {
counter-reset: section;
}
h1::before {
counter-increment: chapter;
content: "Chapter " counter(chapter) ". ";
}
h2::before {
counter-increment: section;
content: counter(chapter) "." counter(section) " ";
} This code defines two counters: chapter and section . Each time an h1 element is encountered, the chapter counter increases and the section counter is reset. Each time an h2 element is encountered, the section counter increases and "XY" is displayed before the h2 element, where X is the current chapter value and Y is the current section value.
When using CSS Counters, we also need to pay attention to some common errors and debugging techniques. For example, if the counter's value does not increase as expected, it may be because the counter is not reset correctly. Make sure to use counter-reset property where appropriate to reset the counter.
In addition, the performance optimization of CSS Counters is also a question worthy of attention. While the performance of CSS Counters itself is not usually a bottleneck, in complex pages, excessive counter operations may affect the rendering speed of the page. Therefore, when using CSS Counters, we should try to simplify the logic of the counter as much as possible and avoid unnecessary counter operations.
Finally, let's take a look at some best practices for using CSS Counters. First, make sure the counter is named clearly and avoid overly complex or confusing names. Secondly, try to define counters in CSS instead of HTML, so as to improve the maintainability and reusability of the code. Finally, use counter-increment and counter-reset properties appropriately to ensure that the counter value is increased and reset correctly.
Through the above, we have gained a deep understanding of CSS Counters. I hope these knowledge and techniques can help you better use CSS Counters in actual projects and create a more beautiful and professional web layout effect.
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