CodePen Embed - Animate Height with CSS calc-size()

<main>
  <section>
    <h1>CSS calc-size() function</h1>
    <p>
      Animate accordion height with new calc-size function.
    </p>
  </section>

  <div class="disclaimer">
    <div class="disclaimer-header">
      <span class="alert-icon">
        <svg xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="1.5" stroke="currentColor" class="size-6">
          <path stroke-linecap="round" stroke-linejoin="round" d="M12 9v3.75m-9.303 3.376c-.866 1.5.217 3.374 1.948 3.374h14.71c1.73 0 2.813-1.874 1.948-3.374L13.949 3.378c-.866-1.5-3.032-1.5-3.898 0L2.697 16.126ZM12 15.75h.007v.008H12v-.008Z" />
        </svg>
      </span>
      <h3>Disclaimer</h3>
      <button type="button" class="close-icon">
        <svg xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24" stroke-width="1.5" stroke="currentColor" class="size-6">
          <path stroke-linecap="round" stroke-linejoin="round" d="M6 18 18 6M6 6l12 12" />
        </svg>
      </button>
    </div>
    <p>
      Currently, <span>calc-size()</span> is only supported in Chrome browsers. To see this demo in action, update Chrome to the latest stable release (129). See <a href="https://caniuse.com/?search=calc-size">caniuse</a> for an overview of browser support.
    </p>
  </div>

  <ul class="accordion-group">
    <!-- Accordion Item -->
    <li class="accordion-item">
      <!-- Button Trigger -->
      <button type="button" class="accordion-trigger">
        <span>Label 1</span>
        <span class="accordion-icon">
          <svg xmlns="http://www.w3.org/2000/svg" class="plus" viewBox="0 0 160 160" fill="currentColor">
            <rect class="vertical-cross" x="70" rx="8" width="15" height="100%" />
            <rect y="70" rx="8" width="100%" height="15" />
          </svg>
        </span>
      </button>
      <!-- Content Container -->
      <div class="accordion-content">
        <p class="contents">
          Cray man braid literally vegan, snackwave polaroid post-ironic. Letterpress fit godard skateboard, street art. Tote bag neutra plaid. Edison bulb tattooed fashion axe.
        </p>
      </div>
    </li>
    <!-- Accordion Item -->
    <li class="accordion-item">
      <!-- Button Trigger -->
      <button type="button" class="accordion-trigger">
        <span>Label 2</span>
        <span class="accordion-icon">
          <svg xmlns="http://www.w3.org/2000/svg" class="plus" viewBox="0 0 160 160" fill="currentColor">
            <rect class="vertical-cross" x="70" rx="8" width="15" height="100%" />
            <rect y="70" rx="8" width="100%" height="15" />
          </svg>
        </span>
      </button>
      <!-- Content Container -->
      <div class="accordion-content">
        <p class="contents">
          Cray man braid literally vegan, snackwave polaroid post-ironic. Letterpress fit godard skateboard, street art. Tote bag neutra plaid. Edison bulb tattooed fashion axe.
        </p>
      </div>
    </li>
    <!-- Accordion Item -->
    <li class="accordion-item">
      <!-- Button Trigger -->
      <button type="button" class="accordion-trigger">
        <span>Label 3</span>
        <span class="accordion-icon">
          <svg xmlns="http://www.w3.org/2000/svg" class="plus" viewBox="0 0 160 160" fill="currentColor">
            <rect class="vertical-cross" x="70" rx="8" width="15" height="100%" />
            <rect y="70" rx="8" width="100%" height="15" />
          </svg>
        </span>
      </button>
      <!-- Content Container -->
      <div class="accordion-content">
        <p class="contents">
          Cray man braid literally vegan, snackwave polaroid post-ironic. Letterpress fit godard skateboard, street art. Tote bag neutra plaid. Edison bulb tattooed fashion axe.
        </p>
      </div>
    </li>
    <!-- Accordion Item -->
    <li class="accordion-item">
      <!-- Button Trigger -->
      <button type="button" class="accordion-trigger">
        <span>Label 4</span>
        <span class="accordion-icon">
          <svg xmlns="http://www.w3.org/2000/svg" class="plus" viewBox="0 0 160 160" fill="currentColor">
            <rect class="vertical-cross" x="70" rx="8" width="15" height="100%" />
            <rect y="70" rx="8" width="100%" height="15" />
          </svg>
        </span>
      </button>
      <!-- Content Container -->
      <div class="accordion-content">
        <p class="contents">
          Cray man braid literally vegan, snackwave polaroid post-ironic. Letterpress fit godard skateboard, street art. Tote bag neutra plaid. Edison bulb tattooed fashion axe.
        </p>
      </div>
    </li>
    <!-- Accordion Item -->
    <li class="accordion-item">
      <!-- Button Trigger -->
      <button type="button" class="accordion-trigger">
        <span>Label 5</span>
        <span class="accordion-icon">
          <svg xmlns="http://www.w3.org/2000/svg" class="plus" viewBox="0 0 160 160" fill="currentColor">
            <rect class="vertical-cross" x="70" rx="8" width="15" height="100%" />
            <rect y="70" rx="8" width="100%" height="15" />
          </svg>
        </span>
      </button>
      <!-- Content Container -->
      <div class="accordion-content">
        <p class="contents">
          Cray man braid literally vegan, snackwave polaroid post-ironic. Letterpress fit godard skateboard, street art. Tote bag neutra plaid. Edison bulb tattooed fashion axe.
        </p>
      </div>
    </li>
  </ul>
</main>

@import url("https://fonts.googleapis.com/css2?family=Inter:ital,opsz,wght@0,14..32,100..900;1,14..32,100..900&display=swap");

:root {
  --text-black: #09080a;
  --text-gray: #3b4b68;
  --highlight: #f1f2f4;
  --disclaimer: #dc2626;
  // --background-discalimer:
}

@layer reset {
  * {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: "Inter", sans-serif;
  }

  body {
    color: var(--text-black);
  }

  ul,
  li {
    list-style: none;
  }

  button {
    border: none;
    background: none;
    appearance: none;
    cursor: pointer;
    white-space: nowrap;
  }

  a {
    text-decoration: none;
  }
}

main {
  width: 100%;
  padding-inline: 1rem;
  padding-bottom: 2rem;
}

section {
  max-width: 64ch;
  gap: 0.5rem 0;
  margin-block: 3rem;

  p {
    color: var(--text-gray);
  }
}

main,
section {
  display: flex;
  flex-direction: column;
  align-items: center;
}

h1 {
  font-size: 2rem;
  letter-spacing: 1px;
}

p {
  line-height: 1.5rem;
}

.disclaimer,
.accordion-group {
  max-width: 420px;
  width: 100%;
}

.disclaimer {
  color: var(--text-gray);
  border: 2px solid var(--disclaimer);
  border-radius: 0.5rem;
  margin-bottom: 1rem;
  padding: 0.75rem;
  display: none;

  &-header {
    display: flex;
    align-items: center;
    gap: 0 0.5rem;
    margin-bottom: 0.5rem;
  }

  h3,
  .alert-icon {
    color: var(--disclaimer);
  }

  .close-icon {
    margin-left: auto;
  }

  .alert-icon,
  .close-icon {
    display: block;
    width: 24px;
    height: 24px;
  }

  p > span {
    font-weight: 600;
  }

  @supports not (height: calc-size(auto, size)) {
    display: block;
  }
}

.accordion-group {
  color: var(--text-gray);
}

.accordion-item + .accordion-item {
  border-top: 2px solid var(--highlight);
}

.accordion-trigger {
  display: flex;
  justify-content: space-between;
  align-items: center;
  width: 100%;
  padding-inline: 0.75rem;
  padding-block: 1rem;
  border-radius: 0.5rem;
  font-size: 1.2rem;
  font-weight: 600;
  color: inherit;

  &:hover {
    background: var(--highlight);
  }

  span {
    display: block;
    flex-shrink: 0;
  }

  .accordion-icon {
    width: 18px;
    height: 18px;
  }

  svg {
    width: 100%;
    height: auto;
  }

  .vertical-cross {
    transition: transform 750ms;
    transform: scaleY(1);
    transform-origin: 50% 50%;

    [data-open] & {
      transform: scaleY(0);
    }
  }
}

.accordion-content {
  height: 0;
  transition-property: height;
  transition-duration: 750ms;
  overflow: hidden;

  .contents {
    padding-inline: 0.75rem;
    padding-top: 0.25rem;
    padding-bottom: 1rem;
  }

  [data-open] & {
    height: auto; // fallback if no support for calc-size
    height: calc-size(auto, size);
  }
}

View Compiled

const accordionTrigger = document.querySelectorAll(".accordion-trigger");

const accordionItem = document.querySelectorAll(".accordion-item");

const closeDisclaimer = document.querySelector(".close-icon");

function toggleAccordion(event) {
  currentTarget = event.target;

  const currentParent = currentTarget.closest(".accordion-item");

  const isOpen = currentParent.hasAttribute("data-open");

  for (let item of accordionItem) {
    item.removeAttribute("data-open");
  }

  if (!isOpen) {
    currentParent.setAttribute("data-open", "");
  }
}

function handleClose() {
  const disclaimer = document.querySelector(".disclaimer");
  disclaimer.style.display = "none";
}

for (let trigger of accordionTrigger) {
  trigger.addEventListener("click", toggleAccordion);
}

closeDisclaimer.addEventListener("click", handleClose);

This Pen is owned by Josh Taylor on CodePen.

See more by @writhisdown on CodePen

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