use-intersection

React Hooks for IntersectionObserver.

:dog: See Storybook.

Installation

$ yarn add use-intersection

Usage

Basic

This is the simplest example.

import React, { useRef } from 'react';
import { useIntersection } from 'use-intersection';

const Component: React.FC = () => {
  const target = useRef<HTMLDivElement>(null);
  const intersecting = useIntersection(target);

  return <div ref={target}>{intersecting ? 'visible' : 'invisible'}</div>;
};

Custom Root Element

This is an example of using scrollable elements other than Viewport.

import React, { useRef } from 'react';
import { useIntersection } from 'use-intersection';

const Component: React.FC = () => {
  const root = useRef<HTMLDivElement>(null);
  const target = useRef<HTMLDivElement>(null);
  const intersecting = useIntersection(target, {
    root,
    rootMargin: '100px',
  });

  return (
    <div style={{ overflow: 'hidden auto', height: 300 }}>
      {/* ... */}
      <div ref={target}>{intersecting ? 'visible' : 'invisible'}</div>
      {/* ... */}
    </div>
  );
};

Lazy Image

This is an example of an Image component that delays loading.

import React, { useRef } from 'react';
import { useIntersection } from 'use-intersection';

const LazyImage: React.FC<React.ComponentProps<'img'>> = (props) => {
  const target = useRef<HTMLSpanElement>(null);
  const intersected = useIntersection(target, {
    rootMargin: '250px',
    once: true,
  });

  return <span ref={target}>{intersected && <img {...props} />}</span>;
};

Browser support

Supports modern web browser.

If your browser does not support IntersectionObserver, we recommend using Polyfill.

npm package

$ yarn add intersection-observer

https://www.npmjs.com/package/intersection-observer

CDN

<script src="https://polyfill.io/v3/polyfill.min.js?features=IntersectionObserverEntry%2CIntersectionObserver"></script>

https://polyfill.io/v3/

API

The following resources will help you.

• React Hooks
• Intersection Observer

---

useIntersection

useIntersection returns a flag whether the target intersects.

const useIntersection = (
  target: React.RefObject<Element> | Element | null,
  options: IntersectionOptions = {},
  callback?: IntersectionChangeHandler,
) => boolean;

options: IntersectionOptions

type IntersectionOptions = {
  root?: React.RefObject<Element>;
  rootMargin?: string;
  threshold?: number | number[];
  once?: boolean;
  defaultIntersecting?: boolean;
};

callback: IntersectionChangeHandler

type IntersectionChangeHandler = (entry: IntersectionObserverEntry) => void;

CHANGELOG

See CHANGELOG.md.

Contributing

We are always welcoming your contribution :clap:

1. Fork (https://github.com/cats-oss/use-intersection) :tada:
2. Create a feature branch :coffee:
3. Run test suite with the $ yarn test command and confirm that it passes :zap:
4. Commit your changes :memo:
5. Rebase your local changes against the master branch :bulb:
6. Create new Pull Request :love_letter:

Bugs, feature requests and comments are more than welcome in the issues.

Development scripts

yarn storybook

Run Storybook.

$ yarn storybook

yarn test

Run Unit test with Jest.

$ yarn test

yarn lint

Run lint with ESLint.

$ yarn lint

yarn format

Run formatting with ESLint (--fix) and Prettier.

$ yarn format

License

MIT © Cyberagent, Inc