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Intersection Observer

<quiet-intersection-observer> stable since 1.0

Watches child elements and dispatches events when they intersect with their root element.

The component uses an IntersectionObserver to monitor when its direct children intersect with a root element. The quiet-intersect event is dispatched when elements enter and leave the viewport.

Scroll to see the element intersect at 100% visibility 
<div id="intersection__overview">
  <quiet-intersection-observer threshold="1" intersect-class="visible">
    <div class="box"><quiet-icon name="bulb"></quiet-icon></div>
  </quiet-intersection-observer>
</div>

<small>Scroll to see the element intersect at 100% visibility</small>

<style>
  /* Container styles */
  #intersection__overview {
    display: flex;
    flex-direction: column;
    gap: 2rem;
    height: 300px;
    border: 2px solid var(--quiet-neutral-stroke-softer);
    border-radius: var(--quiet-border-radius-md);
    padding: 1rem;
    overflow-y: auto;

    /* Spacers to demonstrate scrolling */
    &::before {
      content: '';
      height: 260px;
      flex-shrink: 0;
    }

    &::after {
      content: '';
      height: 260px;
      flex-shrink: 0;
    }   

    /* Box styles */
    .box {
      flex-shrink: 0;
      width: 120px;
      height: 120px;
      border-radius: var(--quiet-border-radius-md);
      background-color: var(--quiet-neutral-fill-softer);
      color: var(--quiet-neutral-text-on-soft);
      display: flex;
      align-items: center;
      justify-content: center;
      margin-inline: auto;
      transition: all 50ms cubic-bezier(0.68, -0.55, 0.265, 1.55);

      quiet-icon {
        font-size: 3rem;
        stroke-width: 1px;
      }

      &.visible {
        background-color: var(--quiet-primary-fill-mid);
        color: var(--quiet-primary-text-on-mid);
      }
    }

    + small {
      display: block;
      text-align: center;
      margin-block-start: 1rem;
    }
  }
</style>

Remember that only direct children of the host element are observed. Nested elements will not trigger intersection events.

Examples Jump to heading

Observing elements Jump to heading

Only direct children of the intersection observer are observed. The component is styled with display: contents , allowing you to easily apply flex and grid layouts to a containing element. 

<div style="display: flex; flex-direction: column;">
  <quiet-intersection-observer>
    <div class="box">Box 1</div>
    <div class="box">Box 2</div>
    <div class="box">Box 3</div>
  </quiet-intersection-observer>
</div>

The component monitors when elements enter and leave the root element (the viewport by default) and dispatches the quiet-intersect event whenever an intersection state changes. The event includes event.detail.entry, which is an IntersectionObserverEntry object containing information about the intersection.

You can determine which element triggered the event with entry.target. You can determine whether an element is entering or leaving the viewport by checking entry.isIntersecting. 

observer.addEventListener('quiet-intersect', event => {
  const entry = event.detail.entry;
  
  if (entry.isIntersecting) {
    console.log('Element entered viewport:', entry.target);
  } else {
    console.log('Element left viewport:', entry.target);
  }
});

Customizing the root Jump to heading

Intersections can be observed within a specific container by setting the root attribute to the ID of the root element . Use root-margin to apply a rootMargin to one or all sides of the element. 

<div id="scroll-container">
  <quiet-intersection-observer 
    root="scroll-container"
    root-margin="50px 0px"
  >
    ...
  </quiet-intersection-observer>
</div>

Providing multiple thresholds Jump to heading

You can monitor different visibility percentages by specifying multiple threshold values separated by a space. 

<quiet-intersection-observer threshold="0 0.25 0.5 0.75 1">
  ...
</quiet-intersection-observer>

Applying classes on intersect Jump to heading

Use the intersect-class attribute to automatically apply the specified class to direct children when they intersect. This makes it easy to style them without event listeners.

Fade In
Slide In
Scale & Rotate
Bounce
Scroll to see elements transition at 50% visibility 
<div id="intersection__classes">
  <quiet-intersection-observer 
    threshold="0.5" 
    intersect-class="visible" 
    root="intersection__classes"
  >
    <div class="box fade">Fade In</div>
    <div class="box slide">Slide In</div>
    <div class="box scale">Scale & Rotate</div>
    <div class="box bounce">Bounce</div>
  </quiet-intersection-observer>
</div>

<small>Scroll to see elements transition at 50% visibility</small>

<style>
  /* Container styles */
  #intersection__classes {
    display: flex;
    flex-direction: column;
    gap: 2rem;
    height: 300px;
    border: 2px solid var(--quiet-neutral-stroke-softer);
    border-radius: var(--quiet-border-radius-md);
    padding: 1rem;
    overflow-y: auto;

    /* Spacers to demonstrate scrolling */
    &::before {
      content: '';
      height: 260px;
      flex-shrink: 0;
    }

    &::after {
      content: '';
      height: 260px;
      flex-shrink: 0;
    }    

    + small {
      display: block;
      text-align: center;
      margin-block-start: 1rem;
    }

    /* Shared box styles */
    .box {
      flex-shrink: 0;
      width: 120px;
      height: 120px;
      border-radius: 8px;
      display: flex;
      align-items: center;
      justify-content: center;
      text-align: center;
      color: white;
      font-weight: bold;
      text-shadow: 0 -0.5px #0008;
      opacity: 0;
      padding: 2rem;
      margin-inline: auto;

      /* Fade */
      &.fade {
        background: linear-gradient(135deg, #5a6fd4 0%, #6a4292 100%);
        transform: translateY(30px);
        transition: all 0.6s ease;

        &.visible {
          opacity: 1;
          transform: translateY(0);
        }
      }

      /* Slide */
      &.slide {
        background: linear-gradient(135deg, #d984e2 0%, #dd4e61 100%);
        transform: translateX(-50px);
        transition: all 0.5s ease;

        &.visible {
          opacity: 1;
          transform: translateX(0);
        }
      }

      /* Scale */
      &.scale {
        background: linear-gradient(135deg, #439be4 0%, #00dae4 100%);
        transform: scale(0.6) rotate(-15deg);
        transition: all 0.7s cubic-bezier(0.175, 0.885, 0.32, 1.275);

        &.visible {
          opacity: 1;
          transform: scale(1) rotate(0deg);
        }
      }

      /* Bounce In and Out */
      &.bounce {
        background: linear-gradient(135deg, #e1658a 0%, #e5cb39 100%);
        opacity: 0;
        transform: scale(0.8);
        transition: none;

        &.visible {
          opacity: 1;
          transform: scale(1);
          animation: bounceIn 0.8s cubic-bezier(0.68, -0.55, 0.265, 1.55) forwards;
        }

        &:not(.visible) {
          animation: bounceOut 0.6s cubic-bezier(0.68, -0.55, 0.265, 1.55) forwards;
        }
      }      
    }
  }

  @keyframes bounceIn {
    0% {
      transform: scale(0.8);
    }
    40% {
      transform: scale(1.08);
    }
    65% {
      transform: scale(0.98);
    }
    80% {
      transform: scale(1.02);
    }
    90% {
      transform: scale(0.99);
    }
    100% {
      transform: scale(1);
    }
  }

  @keyframes bounceOut {
    0% {
      transform: scale(1);
      opacity: 1;
    }
    20% {
      transform: scale(1.02);
      opacity: 1;
    }
    40% {
      transform: scale(0.98);
      opacity: 0.8;
    }
    60% {
      transform: scale(1.05);
      opacity: 0.6;
    }
    80% {
      transform: scale(0.95);
      opacity: 0.3;
    }
    100% {
      transform: scale(0.8);
      opacity: 0;
    }
  }
</style>

Use CSS transitions and animations to create advanced, modern effects without a single line of JavaScript.

An orange cat smiles up at the camera A kitten lays in its bed and cuddles a pillow Two kittens nestled up on a blanket An orange kitten explores a tall grassy yard A kitten peeks out from inside a cardboard box A gray and white cat sleeps on a blanket with evening lights in the background 
<div id="intersection__images">
  <quiet-intersection-observer 
    threshold="0.8" 
    intersect-class="visible"
    root="intersection__images" 
  >
    <img src="https://images.unsplash.com/photo-1671707696618-ca0685b0012e?q=80&w=1000&auto=format&fit=crop&ixlib=rb-4.1.0&ixid=M3wxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8fA%3D%3D" alt="An orange cat smiles up at the camera">
    <img src="https://images.unsplash.com/photo-1736593494119-d0a69181b414?q=80&w=1000&auto=format&fit=crop&ixlib=rb-4.1.0&ixid=M3wxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8fA%3D%3D" alt="A kitten lays in its bed and cuddles a pillow">
    <img src="https://images.unsplash.com/photo-1622576041274-ae5dc580175d?q=80&w=800&auto=format&fit=crop&ixlib=rb-4.1.0&ixid=M3wxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8fA%3D%3D" alt="Two kittens nestled up on a blanket">
    <img src="https://images.unsplash.com/photo-1719310694054-6fc99b7c14ec?q=80&w=1000&auto=format&fit=crop&ixlib=rb-4.1.0&ixid=M3wxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8fA%3D%3D" alt="An orange kitten explores a tall grassy yard">
    <img src="https://images.unsplash.com/photo-1601217156006-3358e1514676?q=80&w=1000&auto=format&fit=crop&ixlib=rb-4.1.0&ixid=M3wxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8fA%3D%3D" alt="A kitten peeks out from inside a cardboard box">    
    <img src="https://images.unsplash.com/photo-1737912031624-e17ba0d7f673?q=80&w=1000&auto=format&fit=crop&ixlib=rb-4.1.0&ixid=M3wxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8fA%3D%3D" alt="A gray and white cat sleeps on a blanket with evening lights in the background">
  </quiet-intersection-observer>
</div>

<style>
  /* Container styles */
  #intersection__images {
    display: flex;
    flex-direction: row;
    gap: 0;
    border: 2px solid var(--quiet-neutral-stroke-softer);
    border-radius: var(--quiet-border-radius-md);
    padding: 1rem;
    overflow-y: auto;
    scroll-snap-type: x mandatory;

    /* Image styles */
    img {
      flex-shrink: 0;
      display: block;
      width: 75%;
      object-fit: cover;
      border-radius: var(--quiet-border-radius-md);
      background-color: var(--quiet-neutral-fill-softer);
      color: var(--quiet-neutral-text-on-soft);
      box-shadow: var(--quiet-shadow-softer);
      filter: grayscale(100%);
      margin-inline: auto;
      transform: scale(0.85) rotateY(-15deg);
      opacity: 0.6;
      transition: all 600ms cubic-bezier(0.25, 0.46, 0.45, 0.94);
      scroll-snap-align: center;

      &.visible {
        background-color: var(--quiet-primary-fill-softer);
        transform: scale(1) rotateY(0deg);
        filter: grayscale(0);
        opacity: 1;
        box-shadow: var(--quiet-shadow-soft);
      }
    }
  }
</style>

API Jump to heading

Importing Jump to heading

The autoloader is the recommended way to import components but, if you prefer to do it manually, the following code snippets will be helpful.

CDN npm

To manually import <quiet-intersection-observer> from the CDN, use the following code. 

import 'https://cdn.jsdelivr.net/npm/@quietui/quiet-browser@1.6.1/dist/components/intersection-observer/intersection-observer.js';

To manually import <quiet-intersection-observer> from npm, use the following code. 

import '@quietui/quiet/components/intersection-observer/intersection-observer.js';

Slots Jump to heading

Intersection Observer supports the following slots. Learn more about using slots

Name Description
(default) The elements to observe. Only direct children of the host element are observed.

Properties Jump to heading

Intersection Observer has the following properties that can be set with corresponding attributes. In many cases, the attribute's name is the same as the property's name. If an attribute is different, it will be displayed after the property. Learn more about attributes and properties

Property / Attribute Description Reflects Type Default
root The ID of the element to use as as the bounding box of the viewport for the observed targets. string
null 		null
rootMargin
root-margin 		Margin around the root. Can have values similar to the CSS margin property. string '0px'
threshold Either a single number or space-delimited numbers which indicate at what percentage of the target's visibility the observer's callback should be executed. string '0'
intersectClass
intersect-class 		A CSS class name to apply to elements while they're intersecting. The class will be removed when the element is no longer in the viewport. This allows you to apply styles to elements as they enter and exit the viewport using pure CSS. string ''
once When true, stops observing after the first intersection. boolean false
disabled Disables the intersection observer. boolean false

Events Jump to heading

Intersection Observer dispatches the following custom events. You can listen to them the same way was native events. Learn more about custom events

Name Description
quiet-intersect Emitted when an observed element starts or stops intersecting. event.detail.entry contains the respective IntersectionObserverEntry object.
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