react-scroll-percentage

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[![License][license-image]][license-url]
[![Downloads][downloads-image]][downloads-url]

React component that reports the current scroll percentage of a element inside
the viewport. Contains both a Hooks, render props and
plain children implementation.

Features

- 🎣 Hooks or Component API - With useScrollPercentage it's easier than
ever to monitor elements
- ⚡️ Optimized performance - Uses
React Intersection Observer
to only update when elements are inside the viewport
- 🌳 Tree-shakeable - Only include the parts you use

Installation

Install using Yarn:

``sh
yarn add react-scroll-percentage
`

or NPM:

`sh
npm install react-scroll-percentage --save
`

> ⚠️ You also want to add the
> intersection-observer
> polyfill for full browser support. Check out adding the polyfill
> for details about how you can include it.

Usage

$3

#### useScrollPercentage

`js
const [ref, percentage] = useScrollPercentage(options)
`

Call the useScrollPercentage hook, with the (optional) options you
need. It will return an array containing a ref, the current scroll
percentage and the current
IntersectionObserverEntry.
Assign the ref to the DOM element you want to monitor, and the hook will
report the status.

`jsx
import React from 'react'
import { useScrollPercentage } from 'react-scroll-percentage'

const Component = () => {
const [ref, percentage] = useScrollPercentage({
/ Optional options /
threshold: 0,
})

return (



)
}
`

$3

To use the component, you pass it a function. It will be
called whenever the user scrolls the viewport, with the new value of
percentage. In addition to the percentage, children also receives a ref
that should be set on the containing DOM element.

If you need it, you can also access the
IntersectionObserverEntry
on entry, giving you access to all the details about the current intersection
state.

`jsx
import { ScrollPercentage } from 'react-scroll-percentage'

const Component = () => (

{({ percentage, ref, entry }) => (


)}

)

export default Component
`

$3

You can pass any element to the , and it will handle
creating the wrapping DOM element. Add a handler to the onChange method, and
control the state in your own component. Any extra props you add the
will be passed to the HTML element, allowing you set the
className, style, etc.

`jsx
import { ScrollPercentage } from 'react-scroll-percentage'

const Component = () => (
as="div"
onChange={(percentage, entry) => console.log('Percentage:', percentage)}
>


Plain children are always rendered. Use onChange to monitor state.

)

export default Component
`

> ⚠️ When rendering a plain child, make sure you keep your HTML output semantic.
> Change the as to match the context, and add a className to style the
> . The component does not support Ref Forwarding, so if
> you need a ref to the HTML element, use the Render Props version instead.

$3

Provide these as props on the component and as the
options argument for the hooks.

| Name | Type | Default | Required | Description |
| --------------- | ------- | ------- | -------- | -------------------------------------------------------------------------------------------------------------------------------------------------------- |
| root | Element | window | false | The Element that is used as the viewport for checking visibility of the target. Defaults to the browser viewport (window) if not specified or if null. |
| rootMargin | string | '0px' | false | Margin around the root. Can have values similar to the CSS margin property, e.g. "10px 20px 30px 40px" (top, right, bottom, left). |
| threshold | number | 0 | false | Number between 0 and 1 indicating the percentage that should be visible before triggering. |
| triggerOnce | boolean | false | false | Only trigger this method once |

$3

The component also accepts the following props:

| Name | Type | Default | Required | Description |
| ------------ | ------------------------------------------------------------ | ------- | -------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| as | string | 'div' | false | Render the wrapping element as this element. Defaults to div. |
| children | ({ref, percentage, entry}) => React.ReactNode, ReactNode | | true | Children expects a function that receives an object containing the percentage boolean and a ref that should be assigned to the element root. Alternatively pass a plain child, to have the deal with the wrapping element. You will also get the IntersectionObserverEntry as entry, giving you more details. |
| onChange | (percentage, entry) => void | | false | Call this function whenever the in view state changes. It will receive the percentage value, alongside the current IntersectionObserverEntry. |

Intersection Observer

Intersection Observer
is the API is used to determine if an element is inside the viewport or not.
Browser support is pretty good -
With
Safari adding support in 12.1,
all major browsers now support Intersection Observers natively.

$3

You can import the
polyfill directly or use
a service like polyfill.io to add it when
needed.

``sh
yarn add intersection-observer
`

Then import it in your app:

`js
import 'intersection-observer'
`

If you are using Webpack (or similar) you could use
dynamic imports, to load
the Polyfill only if needed. A basic implementation could look something like
this:

`js
/**
* Do feature detection, to figure out which polyfills needs to be imported.
**/
async function loadPolyfills() {
if (typeof window.IntersectionObserver === 'undefined') {
await import('intersection-observer')
}
}
``

[package-url]: https://npmjs.org/package/react-scroll-percentage
[npm-version-svg]: https://img.shields.io/npm/v/react-scroll-percentage.svg
[npm-minzip-svg]: https://img.shields.io/bundlephobia/minzip/react.svg
[bundlephobia-url]: https://bundlephobia.com/result?p=react-scroll-percentage
[deps-svg]: https://david-dm.org/thebuilder/react-scroll-percentage.svg
[deps-url]: https://david-dm.org/thebuilder/react-scroll-percentage
[dev-deps-svg]:
https://david-dm.org/thebuilder/react-scroll-percentage/dev-status.svg
[dev-deps-url]:
https://david-dm.org/thebuilder/react-scroll-percentage#info=devDependencies
[license-image]: http://img.shields.io/npm/l/react-scroll-percentage.svg
[license-url]: LICENSE
[downloads-image]: http://img.shields.io/npm/dm/react-scroll-percentage.svg
[downloads-url]: http://npm-stat.com/charts.html?package=react-scroll-percentage