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https://github.com/jscottsmith/react-observed
👀 React component using the browser's Intersection Observer API to watch for when an element is within (or intersecting with) the viewport.
https://github.com/jscottsmith/react-observed
component intersection observer react viewport watch waypoints
Last synced: about 2 months ago
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👀 React component using the browser's Intersection Observer API to watch for when an element is within (or intersecting with) the viewport.
- Host: GitHub
- URL: https://github.com/jscottsmith/react-observed
- Owner: jscottsmith
- License: mit
- Created: 2017-10-17T18:22:10.000Z (about 7 years ago)
- Default Branch: master
- Last Pushed: 2022-12-09T17:13:09.000Z (about 2 years ago)
- Last Synced: 2024-10-31T19:24:39.818Z (2 months ago)
- Topics: component, intersection, observer, react, viewport, watch, waypoints
- Language: JavaScript
- Homepage: http://react-observed.surge.sh/
- Size: 3.85 MB
- Stars: 22
- Watchers: 4
- Forks: 1
- Open Issues: 23
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# React Observed
[](https://badge.fury.io/js/react-observed) [](https://travis-ci.org/jscottsmith/react-observed) [](https://codecov.io/gh/jscottsmith/react-observed)
React component using the browser's Intersection Observer API to watch for when an element is within (or intersecting with) the viewport.
## Example
[Storybook Demos](http://react-observed.surge.sh/)
## Install
```
npm install react-observed --save
```
or with Yarn
```
yarn add react-observed
```
**Note:** For complete [browser support](#browser-support) you must also provide an [Intersection Observer polyfill](https://github.com/w3c/IntersectionObserver/tree/master/polyfill).
```
npm install intersection-observer --save
```
or
```
yarn add intersection-observer
```
## Usage
`` takes a function as a child which gives you access to the `isInView` and `mapRef` properties.
`mapRef` is the ref function callback that must be declared on the observed target element like `
`. Then `isInView` will give you the current state of the observed element.
Here's an example:
```jsx
{({ isInView, mapRef }) => (
{isInView ? (
I'm in view!
) : (
I'm not in view
)}
)}
```
## \ Props
`` takes the props as shown by the following example:
```jsx
{}} // handler called with the current `isInView` state whenever it changes
onEnter={() => {}} // handler called when the observed element enters
onExit={() => {}} // handler called when the observed element exits
onIntersect={entry => {}} // handler called when each threshold is met with the entry data
options={{
// IntersectionObserver constuctor options
root: null,
rootMargin: "0px",
threshold: 0.5
}}
/>
```
| Name | Type | Default | Description |
| --------------------- | :--------: | :---------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **initialViewState** | `Boolean` | `false` | Optionally sets the initial `isInView` state. By default this is `false` until the observer updates the state. |
| **intersectionRatio** | `Number` | `0` | The intersection ratio (a value between `0–1`) that when `>=` to the target's intersect ratio and not equal to `0` will be considered in view. |
| **once** | `Boolean` | `false` | If once is `true` the observer will disconnect after the target element has entered the view. Useful for triggering something when in view for a single time. |
| **onChange** | `Function` | | Handler to be called with the current `isInView` state whenever it changes. |
| **onEnter** | `Function` | | Handler to be called when the `isInView` state changes to `true`. |
| **onExit** | `Function` | | Handler to be called when the `isInView` state changes to `false`. |
| **onIntersect** | `Function` | | Handler to be called when each threshold is met with the current [entry](https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserverEntry) data. |
| **options** | `Object` | \*see below | Options passed to the IntersectionObserver constructor. |
### \*IntersectionObserver Options
These are the options passed to the [IntersectionObserver constructor](https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API#Creating_an_intersection_observer). The default `options` to the `` component are:
```js
options: {
root: null,
rootMargin: '0px',
threshold: [0],
}
```
The following is as described on MDN:
| Name | Type | Default | Description |
| -------------- | :-----------------: | :------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **root** | `Element` | `null` | The DOM element that is used as the viewport for checking visiblity of the target. Must be the ancestor of the target. Defaults to the browser viewport if not specified or if `null`. |
| **rootMargin** | `String` | `0px` | Margin around the root. Can have values similar to the CSS margin property, e.g. `10px 20px 30px 40px` (top, right, bottom, left). If the root element is specified, the values can be percentages. This set of values serves to grow or shrink each side of the root element's bounding box before computing intersections. Defaults to all zeros. |
| **threshold** | `Number` or `Array` | `[0]` | Either a single `Number` or an `Array` of numbers which indicate at what percentage of the target's visibility the observer's callback should be executed. If you only want to detect when visibility passes the 50% mark, you can use a value of `0.5`. If you want the callback run every time visibility passes another 25%, you would specify the array `[0, 0.25, 0.5, 0.75, 1]`. The default is `0` (meaning as soon as even one pixel is visible, the callback will be run). A value of `1.0` means that the threshold isn't considered passed until every pixel is visible. |
## Render Callback
The child function takes one object parameter like such `{ isInView, mapRef }`. It's required to map a ref function to a DOM element otherwise `` will throw an error.
Example:
```jsx
{({ mapRef }) =>
}
```
The keys of which are:
| Name | Type | Description |
| ------------ | :--------: | --------------------------------------------------------------------------------------------------------------------------------------- |
| **isInView** | `Boolean` | This is `true` when the observed element's intersection ratio is `>=` to the `intersectionRatio` prop. |
| **mapRef** | `Function` | This a `function` that is declared as the `ref` of the DOM element to be observed. Note that this is required for the observer to work. |
## Browser Support
Intersection Observer is [supported](https://caniuse.com/#feat=intersectionobserver) by the latest major browsers. For older browsers a [good polyfill](https://github.com/w3c/IntersectionObserver/tree/master/polyfill) is necessary.