npm package discovery and stats viewer.

Discover Tips

  • General search

    [free text search, go nuts!]

  • Package details

    pkg:[package-name]

  • User packages

    @[username]

Sponsor

Optimize Toolset

I’ve always been into building performant and accessible sites, but lately I’ve been taking it extremely seriously. So much so that I’ve been building a tool to help me optimize and monitor the sites that I build to make sure that I’m making an attempt to offer the best experience to those who visit them. If you’re into performant, accessible and SEO friendly sites, you might like it too! You can check it out at Optimize Toolset.

About

Hi, 👋, I’m Ryan Hefner  and I built this site for me, and you! The goal of this site was to provide an easy way for me to check the stats on my npm packages, both for prioritizing issues and updates, and to give me a little kick in the pants to keep up on stuff.

As I was building it, I realized that I was actually using the tool to build the tool, and figured I might as well put this out there and hopefully others will find it to be a fast and useful way to search and browse npm packages as I have.

If you’re interested in other things I’m working on, follow me on Twitter or check out the open source projects I’ve been publishing on GitHub.

I am also working on a Twitter bot for this site to tweet the most popular, newest, random packages from npm. Please follow that account now and it will start sending out packages soon–ish.

Open Software & Tools

This site wouldn’t be possible without the immense generosity and tireless efforts from the people who make contributions to the world and share their work via open source initiatives. Thank you 🙏

© 2024 – Pkg Stats / Ryan Hefner

@locmod/intersection-observer

v1.0.1

Published

IntersectionObserver react hooks

Downloads

223

Readme

intersection-observer

Features

  • Lazy loading of images or other content as the page scrolls.
  • Implementation of "infinity scrolling" sites, where new content is loaded and displayed as you scroll.
  • Reporting on the visibility of the site's promotional blocks to calculate effectiveness.
  • Deciding whether to perform tasks or animations depending on whether the user sees the result.

W3C Documentation

API

Polyfill

Library has a polyfill taken from W3C (which was moved and archived in GoogleChromeLabs/intersection-observer).

The polyfill isn't included into the bundle. If you need to support old browsers, call requirePolyfill on client app initialization to verify if client needs it and require dynamically the polyfill script. It should be done before App become interactive, use callback for more control.

// client
import { requirePolyfill } from '@locmod/intersection-observer'


requirePolyfill(() => {
  setIntersectionObserverReady(true)
  renderApp()
  whatever()
})

Or use polyfill.io instead:

<script src="https://polyfill.io/v3/polyfill.min.js?features=IntersectionObserver"></script>

useEntry

Calls rerender on each change of entry state.

const [ ref, entry, unobserve ] = useEntry(options)

useEntryListener

Entry changes call listener callback, it doesn't have a state, so doesn't rerender a component.

const listener = (entry: IntersectionObserverEntry) => {}

const [ ref, unobserve ] = useEntryListener(listener, options)

options

{
  // IntersectionObserver options
  observerProps: {
    root: node,
    rootMargin: '10px 10px 10px 10px',
    threshold: [ 0, 0.25, 0.5, 0.75, 1 ],
  },
  // event will be fired once and then unsubscribed from observer
  once: true,
}

Read more about IntersectionObserver options.

Examples

Hide an element when footer is in viewport

const App = () => {
  const [ ref, entry ] = useEntry()
  
  const isVisible = !entry || !entry.isIntersecting

  return (
    <div>
      <Element isVisible={isVisible} />
      <div ref={ref} />
      <Footer />
    </div>
  )
}

Lazy images

Add rootMargin: '50%' to start loading and rendering the image when there is half the height of the viewport before the image becomes visible, so when the image appears in the viewport it will not blink. Add once: true because the image should be processed only once.

const LazyImage = ({ src }) => {
  const [ ref, entry ] = useEntry({
    observerProps: { rootMargin: '50%' },
    once: true,
  })

  const finalSrc = entry && entry.isIntersecting ? src : 'placeholder.jpg'

  return (
    <img ref={ref} src={finalSrc} />
  )
}

const App = () => (
  <>
    <div style={{ height: '150vh', backgroundColor: '#face8D' }} />
    <LazyImage key={src} src={src} />
  </>
)

Trigger a callback

For example, to trigger an analytical event if a client sees an element (it works for both cases: vertical and horizontal scroll, e.g. carousel of banners)

const Component = () => {
  const [ ref ] = useEntryListener(() => {
    track('The element shown')
  }, { once: true })

  return (
    <div ref={ref} />
  )
}