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react-visibility-observer

React component for watching when an element is visible in the viewport.

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Popularity

Downloads/wk

9

GitHub Stars

11

Maintenance

Last Commit

1yr ago

Contributors

0

Package

Dependencies

0

Size (min+gzip)

0.7KB

License

MIT

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Categories

Readme

Description

React component using the Intersection Observer API for watching when an element is visible in the viewport.

Written in TypeScript using React Hooks and Context. No dependencies.

github license npm version npm bundle size downloads react

Install

with Yarn

yarn add react-visibility-observer

or with NPM

npm install --save react-visibility-observer

Usage

// Component.tsx

import VisibilityObserver from 'react-visibility-observer'

const Component: React.FC = () => (
  <VisibilityObserver>
    <ChildComponent />
  </VisibilityObserver>
)
// ChildComponent.tsx

import { useVisibilityObserver } from 'react-visibility-observer'

const ChildComponent: React.FC = () => {
  const { isVisible } = useVisibilityObserver()

  return <div>{isVisible ? "I'm visible!" : "I'm hidden!"}</div>
}

Component

You can configure the VisibilityObserver component by passing in the following props.

const Component: React.FC = () => (
  <VisibilityObserver
    className="myClass"
    triggerOnce={true}
    root={document.querySelector('#scrollArea')}
    rootMargin="50px 50px 50px 50px"
    threshold={0.2}
  >
    <ChildComponent />
  </VisibilityObserver>
)
Prop TypeDescription
classNamestringCustom class for the tracked div. Defaults to no class name.
triggerOncebooleanTrigger observer only once when the element becomes available. Defaults to false.
rootElement or nullThe element that is used as the viewport for checking visiblity of the target. Must be the ancestor of the target. Defaults to null which is the browser viewport.
rootMarginstringMargin around the root. Can have values similar to the CSS margin property, e.g. "10px 20px 30px 40px" (top, right, bottom, left). The values can be percentages. This set of values serves to grow or shrink each side of the root element's bounding box before computing intersections. Defaults to "0 0 0 0".
thresholdnumber or number[]Either a single number or an array of numbers which indicate at what percentage of the target's visibility the observer's callback should be executed. If you only want to detect when visibility passes the 50% mark, you can use a value of 0.5. If you want the callback to run every time visibility passes another 25%, you would specify the array [0, 0.25, 0.5, 0.75, 1]. The default is 0 (meaning as soon as even one pixel is visible, the callback will be run). A value of 1.0 means that the threshold isn't considered passed until every pixel is visible.

Hook

You can get info from the observer by using the useVisibilityObserver hook in the child components.

const { isVisible, entries } = useVisibilityObserver()
 Variable TypeDescription
 isVisiblebooleanIs the observed element in view.
 entriesIntersectionObserverEntry[]Array of IntersectionObserverEntry objects being observed.

Browser Support

Intersection Observer API is compatible with all modern browsers. If you need support for older browsers, use the polyfill by W3C.

Install the polyfill with Yarn

yarn add intersection-observer

or with NPM

npm install --save intersection-observer

and add to the top of your client's entry point

// Browser.tsx

import 'intersection-observer'

Contribute

Use GitHub issues and Pull Requests.

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