HeightAnimation#

Import#

import { HeightAnimation } from '@dnb/eufemia'

Description#

The HeightAnimation component calculates the height, and animates from auto to auto – or from 0 to auto in height – powered by CSS transition. It calculates the height on the fly.

When the animation is done, it sets the element's height to auto.

The component can be used as an opt-in replacement instead of vanilla HTML Elements.

The element animation is done with a CSS transition with 400ms in duration.

It also re-calculates and changes the height, when the given content changes.

Relevant links#

Server-side rendering (SSR)#

HeightAnimation is SSR-compatible. When open is true (the default), the component renders its content with the --is-visible class during server-side rendering so the initial HTML is correct without waiting for JavaScript.

Custom duration and delay props are applied after hydration via a DOM effect to avoid hydration mismatches caused by differences in how React serializes CSS custom properties on the server versus the client.

Accessibility#

Connect the control and animated content with aria-controls, and expose the current state with aria-expanded. HeightAnimation does not manage focus. Avoid closing content while focus is inside it, or move focus to a logical visible control first.

When keepInDOM or openOnFind keeps closed content in the DOM, HeightAnimation applies aria-hidden="true". The collapsed content is therefore unavailable to assistive technologies until it opens.

openOnFind uses the native hidden="until-found" behavior, making collapsed text available to browser find-in-page. HeightAnimation opens matching content internally, so onBeforeMatch is optional. When an external control owns the open state, handle onBeforeMatch by updating the same state passed to open. This keeps the control's aria-expanded value synchronized when the browser reveals a match.

openOnFind depends on native browser support for hidden="until-found"; see MDN for details and current compatibility. In browsers without support, it falls back to keepInDOM behavior: the content remains mounted and hidden, but is unavailable to browser find-in-page.

Users who prefer reduced motion receive an effectively immediate transition. It is important to never animate to a fixed height such as 64px, because:

The content may differ based on the viewport width (screen size)
The content itself may change
The user may have a larger font-size

Related components#

HeightAnimation is part of the Other category. Other components for similar needs:

CopyOnClick — when people should copy text by clicking it.
PortalRoot — to render floating content outside the normal page structure.
ScrollView — when content needs its own horizontal or vertical scrolling area.

Demos#

Animation during height changes#

This example shows how you easily can enhance the user experience. Here we also use showOverflow to avoid hidden overflow during the animation.

Look at me 👀

const Example = () => {
  const [showMe, setShowMe] = useState(true)
  return (
    <>
      <HeightAnimation showOverflow>
        {showMe ? (
          <Button
            onClick={() => {
              setShowMe(!showMe)
            }}
          >
            Click me!
          </Button>
        ) : (
          <Anchor
            onClick={() => {
              setShowMe(!showMe)
            }}
          >
            No, click me!
          </Anchor>
        )}
      </HeightAnimation>

      <P top>Look at me 👀</P>
    </>
  )
}
render(<Example />)

Basic open/close#

This example removes its given children, when open is open={false}.

Look at me 👀

const Example = () => {
  const [openState, setOpenState] = useState(false)
  const [contentState, setContentState] = useState(false)
  const onChangeHandler = ({ checked }) => {
    setOpenState(checked)
  }
  return (
    <>
      <ToggleButton checked={openState} onChange={onChangeHandler} right>
        Open/close
      </ToggleButton>
      <ToggleButton
        checked={contentState || !openState}
        disabled={!openState}
        onChange={({ checked }) => {
          setContentState(checked)
        }}
        space={{
          top: true,
          bottom: true,
        }}
      >
        Change height inside
      </ToggleButton>

      <Section variant="information" top>
        <HeightAnimation open={openState}>
          <Section
            innerSpace={{
              block: 'large',
            }}
            variant="information"
          >
            <P space={0}>Your content</P>
          </Section>
          {contentState && <P space={0}>More content</P>}
        </HeightAnimation>
      </Section>

      <P top>Look at me 👀</P>
    </>
  )
}
render(<Example />)

Keep in DOM#

When providing keepInDOM={true}, your nested content will never be removed from the DOM. But rather be "hidden" with visually: hidden and aria-hidden.

Your content

const Example = () => {
  const [openState, setOpenState] = useState(true)
  const [contentState, setContentState] = useState(false)
  const onChangeHandler = ({ checked }) => {
    setOpenState(checked)
  }
  return (
    <>
      <ToggleButton checked={openState} onChange={onChangeHandler} right>
        Open/close
      </ToggleButton>
      <ToggleButton
        checked={contentState || !openState}
        disabled={!openState}
        onChange={({ checked }) => {
          setContentState(checked)
        }}
        space={{
          top: true,
          bottom: true,
        }}
      >
        Change height inside
      </ToggleButton>

      <StyledSection variant="information" top>
        <HeightAnimation open={openState} keepInDOM={true} duration={1000}>
          <Section
            innerSpace={{
              block: 'large',
            }}
            variant="information"
          >
            <P space={0}>Your content</P>
          </Section>
          {contentState && <P space={0}>More content</P>}
        </HeightAnimation>
      </StyledSection>
    </>
  )
}
const StyledSection = styled(Section)`
  .content-element {
    transition: transform 1s var(--easing-default);
    transform: translateY(-2rem);

    padding: 4rem 0;
  }

  .dnb-height-animation--parallax .content-element {
    transform: translateY(0);
  }
`
render(<Example />)

Find collapsed content#

The openOnFind prop keeps collapsed content available to the browser's find-in-page feature using hidden="until-found". Search this page for “Findable banking content”. HeightAnimation opens the match itself, while the optional onBeforeMatch callback synchronizes the toggle's external state.

const Example = () => {
  const [openState, setOpenState] = useState(false)
  return (
    <>
      <ToggleButton
        checked={openState}
        aria-expanded={openState}
        aria-controls="open-on-find-content"
        onChange={({ checked }) => setOpenState(checked)}
      >
        Open content
      </ToggleButton>

      <HeightAnimation
        id="open-on-find-content"
        open={openState}
        openOnFind
        onBeforeMatch={() => setOpenState(true)}
      >
        <Space innerSpace>
          <Section variant="information" innerSpace>
            <P space={0}>Findable banking content</P>
          </Section>
        </Space>
      </HeightAnimation>
    </>
  )
}
render(<Example />)

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