A Guide to CSS counter

A Guide to CSS counter

Use the “counter" property to turn any element into a numbered list. Similar to how the ordered list tag works

    . Very useful if you’re creating a documentation site where you need to automatically number the headings or create a table of contents 👍
    div {
    /* Define & Initialize Counter */
    counter-reset: tidbit-counter;
    }

    h2::before {
    /* Increment Counter */
    counter-increment: tidbit-counter;

    /* Display Counter */
    content: counter(tidbit-counter) ": ";
    }

    <div>
    <h2>HTML</h2>
    <h2>CSS</h2>
    <h2>JS</h2>
    </div>

    How the counter property work

    There are 3 steps to get the counter to work:

    Define & Initialize Counter
    Increment Counter
    Display Counter

    1. Define & Initialize Counter

    There are 2 parts to this step. You need to define your counter and give it a name.
    1a. Define Counter
    I have named mine tidbit-counter. We give it a name so we can call it in the later steps.
    counter-reset: tidbit-counter;

    1b. Initialize Counter
    The next part is to initialize your counter. By default, the value of this is 0. Note, this number is not displayed. This is just where you setting the "starting" of your counter. So if I had set this number to be 20, then my output would go 21, 22, 23…etc. Assuming that my increment is 1 (more on this later).

    counter-reset
    Output

    0
    1, 2, 3 …etc

    20
    21, 22, 23…etc

    58
    59, 60, 61…etc

    Here’s an example:
    div {
    counter-reset: tidbit-counter 58; /* 👈 */
    }

    h2::before {
    counter-increment: tidbit-counter;
    content: counter(tidbit-counter) ": ";
    }

    <div>
    <h2>HTML</h2>
    <h2>CSS</h2>
    <h2>JS</h2>
    </div>

    59: HTML
    60: CSS
    61: JS

    Where to apply the counter-rest property?
    You want to apply the counter-reset property on the parent element. Here’s what happens if you don’t apply it to the parent.
    /* ❌ Wrong */
    h2 {
    counter-reset: tidbit-counter;
    }

    h2::before {
    counter-increment: tidbit-counter;
    content: counter(tidbit-counter) ": ";
    }

    And here’s the output. As you noticed, it doesn’t increment properly 🙁
    1: HTML
    1: CSS
    1: JS

    Also, it doesn’t have to be the direct parent. As long as it’s an HTML element that wraps your counter list. You’re good. Like this:
    <section>
    <div>
    <h2>HTML</h2>
    <h2>CSS</h2>
    <h2>JS</h2>
    </div>
    </section>

    /* ✅ This works */
    section {
    counter-reset: tidbit-counter;
    }

    1: HTML
    2: CSS
    3: JS

    2. Increment Counter

    Once you set up your counter. Now you can start incrementing it. Here’s the syntax for this property:
    counter-rest: <counter name> <integer>

    As you noticed, it accepts an integer argument. That means you are not restricted to just increasing the counter value by 1. Below chart assumes counter-reset is 0.

    counter-increment
    Output

    1 (default)
    1, 2, 3 …etc

    5
    5, 10, 15…etc

    -5
    -5, -10, -15…etc

    And yes, you can also pass in a negative integer to decrease the counter. Okay, let’s see how that would be implemented:
    div {
    counter-reset: tidbit-counter;
    }

    h2::before {
    counter-increment: tidbit-counter -5; /* 👈 */
    content: counter(tidbit-counter) ": ";
    }

    <div>
    <h2>HTML</h2>
    <h2>CSS</h2>
    <h2>JS</h2>
    </div>

    -5: HTML
    -10: CSS
    -15: JS

    3. Display Counter

    Finally, to display the counter, we need to pass the counter function as the value for our content property. The content property is often the way for us to display value in our HTML through CSS. Here’s the syntax for our counter function.
    counter(<counter name>, <counter list style>)

    By default, we have been working numbers. And that’s the default counter list style or in the docs, they call it style. But you can also pass in other styles.

    style
    Output

    default
    1, 2, 3 …etc

    upper-alpha
    A, B, C …etc

    lower-roman
    i, ii, iii …etc

    thai
    ๑, ๒, ๓ …etc

    You can see the full list of styles here
    And let’s look at an example:
    div {
    counter-reset: tidbit-counter;
    }

    h2::before {
    counter-increment: tidbit-counter;
    content: counter(tidbit-counter, thai); /* 👈 */
    }

    <div>
    <h2>HTML</h2>
    <h2>CSS</h2>
    <h2>JS</h2>
    </div>

    ๑HTML
    ๒CSS
    ๓JS

    Multiple Counters

    You can also set multiple counters just by simply defining another counter name.
    div {
    counter-reset: counter-one counter-two 100; /* 👈 */
    }

    h2::before {
    counter-increment: counter-one;
    content: counter(counter-one) ": ";
    }

    h3::before {
    counter-increment: counter-two;
    content: counter(counter-two) ": ";
    }

    <div>
    <h2>one</h2>
    <h2>one</h2>

    <h3>two</h3>
    <h3>two</h3>
    </div>

    1: one
    2: one

    101: two
    102: two

    Nested Counter

    You can also set a nested counter. Instead of using counter, you use the plural form counters. The counters accept an additional argument:
    counter(<counter name>, <string>, <counter list style>)

    The string argument is a string separator that you use to indicated how you want to separate the list item for nested counters.

    string
    Output

    "."
    1.1, 1.2, 1.3 …etc

    ">"
    1>1, 1>2, 1>3 …etc

    ":"
    1:1, 1:2, 1:3 …etc

    Let’s look at an example:
    div {
    counter-reset: multi-counters;
    }

    h2::before {
    counter-increment: multi-counters;
    content: counters(multi-counters, ".") ": ";
    }

    <div>
    <h2>Frameworks</h2>
    <div>
    <h2>Vue</h2>
    <h2>React</h2>
    <h2>Angular</h2>
    </div>
    </div>

    1: Frameworks
    1.1: Vue
    1.2: React
    1.3: Angular

    counter vs <ol>

    CSS counter doesn’t replace <ol>. If you have a numbered ordered list, then you should absolutely still use <ol> because it’s important that you structure your HTML using the proper semantics. Semantic markup is crucial for Accessibility and SEO.
    <ol> for the win
    Here’s an example where I should use <ol>. In this instance, I’m just listing a bunch of rules. It makes semantic sense to use an ordered list <ol>.
    <h2>Rules</h2>

    <ol>
    <li>You do not talk about Fight Club</li>
    <li>You do not talk about Fight Club</li>
    </ol>

    CSScounter for the win
    Here’s an example where I would use CSS counter. In this instance, I have a documentation page using headings h2 and paragraphs p. In this example, having a counter is more of a visual presentation. This example would make sense using CSS counter.
    <article>
    <h2>What is Vue.js?</h2>
    <p>Vue is a progressive framework for building user interfaces.</p>

    <h2>Getting Started</h2>
    <p>Visit Vuejs.org to learn more!</p>
    </article>

    1: What is Vue.js?
    Vue is a progressive framework for building user interfaces.

    2: Getting Started
    Visit Vuejs.org to learn more!

    ☝️Can you tell I really like Vue.js 😝

    Browser Support

    The CSS counter is supported by all major browsers including Internet Explorer 8 and above.
    Can I Use: CSS Counters

    Resources

    MDN Web Docs: Using CSS counters
    MDN WebDocs: List Style Type
    w3schools: CSS counter-increment
    w3schools: CSS counter-reset
    CSS Tricks: counter-increment
    CSS Tricks: counter-reset
    30 Seconds of CSS
    Counters and Calc(): Two Little-Known CSS Features Explained
    The Accessibility of ::before and ::after
    Accessiblity support for CSS generated content

    Thanks for reading ❤
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    Link: https://dev.to/samanthaming/a-guide-to-css-counter-3aaa