intersection observed

[](https://www.npmjs.com/package/@nju33/react-intersection-observed])

Install

yarn add @nju33/react-intersection-observed

yarn add react react-dom @types/react @types/react-dom

Example

import intersectionObservedFactory = require('@nju33/react-intersection-observed');
import {
  IntersectionObservedProps,
  IntersectionObservedComponent,
  IntersectionObserved
} from '@nju33/react-intersection-observed';

interface FooProps {
  foo: string;
}

type FooIntersectionProps = FooProps & IntersectionObservedProps

class Foo extends React.Component<FooIntersectionProps>
  implements IntersectionObservedComponent {
  render() {
    return <div ... />;
  }

  // optional
  componentOnEnter() {
    console.log('componentOnEnter');
  }

  // optional
  componentOnceEnter() {
    console.log('componentOnceEnter');
  }

  // optional
  componentOnLeave() {
    console.log('componentOnLeave');
  }

  // optional
  componentOnceLeave() {
    console.log('componentOnceLeave');
  }

  componentWillUnmount() {
    this.props.intersectionObserved.unobserve();
  }
}

const intersectionObserved = intersectionObservedFactory();
const IntersectionObservedFoo = (intersectionObserved as IntersectionObserved<FooProps>)(Foo);

<IntersectionObservedFoo foo="foooo" />

With the StyledComponents

If you have used styled-components, you've to apply intersectionObservedearlier than styled.

e.g.

const IntersectionObservedFoo = (intersectionObserved as IntersectionObserved<
  FooProps
>)(Foo);
const styledFoo = styled(IntersectionObservedFoo);

<styledFoo foo="fooooo" />;

Customize

you can adjust determine when an element entered into the view. For that you've to set the isEnter function in the argument object of the intersectionObservedFactory.

// intersectionObservedFactory({
//   isEnter(entry: IntersectionObserverEntry): boolean;
// })
intersectionObservedFactory({
  isEnter(entry: IntersectionObserverEntry) => entry.intersectionRatio !== 0;
})