React In Viewport

Library to detect whether or not a component is in the viewport, using the [Intersection Observer API](https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API). This library also uses [MutationObserver](https://developer.mozilla.org/en-US/docs/Web/API/MutationObserver) to detect the change of the target element. ```npm install --save react-in-viewport``` ```yarn add react-in-viewport``` ## Examples [Demo](https://roderickhsiao.github.io/react-in-viewport/) ## Why A common use case is to load an image when a component is in the viewport ([lazy load](https://medium.com/@roderickhsiao/performance-101-i-know-how-to-load-images-a262d556250f)). We have traditionally needed to monitor scroll position and calculate the viewport size, which can be a scroll performance bottleneck. Modern browsers now provide a new API--[Intersection Observer API](https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API)--which can make implementating this effort much easier and performant. ## Polyfill For browsers not supporting the API, you will need to load a [polyfill](https://www.npmjs.com/package/intersection-observer). [Browser support table](https://caniuse.com/#feat=intersectionobserver) ```js require('intersection-observer'); ``` ## Design The core logic is written using React Hooks. We provide two interfaces: you can use `handleViewport`, a higher order component (HOC) for class based components, or use hooks directly, for functional components. The HOC acts as a wrapper and attaches the intersection observer to your target component. The HOC will then pass down extra props, indicating viewport information and executing a callback function when the component enters and leaves the viewport. ## Usages ### Using Higher Order Component When wrapping your component with `handleViewport` HOC, you will receive `inViewport` props indicating whether the component is in the viewport or not. `handleViewport` HOC accepts three params: `handleViewport(Component, Options, Config)` | Params | Type | Description | |-----------|---------------|------------------------------------------------------------------------------------------------------------------------------------| | Component | React Element | Callback function for when the component enters the viewport | | Options | Object | Options you want to pass to [Intersection Observer API](https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API) | | | Config | Object | Configs for HOC (see below) | ### Supported config | Params | Type | Default | Description | |-------------------|---------|------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------| | disconnectOnLeave | boolean | false | Disconnect intersection observer after leave | ### HOC Component Props | Props | Type | Default | Description | |-----------------|----------|---------|-------------------------------------------------| | onEnterViewport | function | | Callback function for when the component enters the viewport | | onLeaveViewport | function | | Callback function for when the component leaves the viewport | The HOC preserves `onEnterViewport` and `onLeaveViewport` props as a callback ### Props passed down by HOC to your component | Props | Type | Default | Description | |------------|-----------|---------|-----------------------------------------------------------------------------------| | inViewport | boolean | false | Whether your component is in the viewport | | forwardedRef | React ref | | Assign this prop as a ref on your component | | enterCount | number | | Numbers of times your component has entered the viewport | | leaveCount | number | | Number of times your component has left the viewport | _NOTE_: Need to add `ref={this.props.forwardedRef}` to your component #### Example of a functional component ```tsx import handleViewport, { type InjectedViewportProps } from 'react-in-viewport'; const Block = (props: InjectedViewportProps) => { const { inViewport, forwardedRef } = props; const color = inViewport ? '#217ac0' : '#ff9800'; const text = inViewport ? 'In viewport' : 'Not in viewport'; return (

{ text }

); }; const ViewportBlock = handleViewport(Block, /** options: {}, config: {} **/); const Component = (props) => (

Scroll down to make component in viewport

console.log('enter')} onLeaveViewport={() => console.log('leave')} />

)) ``` #### Example for enter/leave counts - If you need to know how many times the component has entered the viewport, use the prop `enterCount`. - If you need to know how many times the component has left the viewport, use the prop `leaveCount`. ```javascript import React, { Component } from 'react'; import handleViewport from 'react-in-viewport'; class MySectionBlock extends Component { getStyle() { const { inViewport, enterCount } = this.props; //Fade in only the first time we enter the viewport if (inViewport && enterCount === 1) { return { WebkitTransition: 'opacity 0.75s ease-in-out' }; } else if (!inViewport && enterCount < 1) { return { WebkitTransition: 'none', opacity: '0' }; } else { return {}; } } render() { const { enterCount, leaveCount, forwardedRef } = this.props; return (

Hello

{`Enter viewport: ${enterCount} times`}

{`Leave viewport: ${leaveCount} times`}

); } } const MySection = handleViewport(MySectionBlock, { rootMargin: '-1.0px' }); export default MySection; ``` ### Using Hooks Alternatively, you can also directly using `useInViewport` hook which takes similar configuration as HOC. ```js import React, { useRef } from 'react'; import { useInViewport } from 'react-in-viewport'; const MySectionBlock = () => { const myRef = useRef(null); const { inViewport, enterCount, leaveCount, } = useInViewport( myRef, options, config = { disconnectOnLeave: false }, props ); return (

Hello

{`Enter viewport: ${enterCount} times`}

{`Leave viewport: ${leaveCount} times`}

); }; ``` ## Who is using this component - [Tinder](https://tinder.com)

パッケージ	ダウンロード数	Stars	サイズ	Issues	公開日時	ライセンス

react-in-viewport	36,019	350	110 kB	3	5ヶ月前	MIT