Monitor if a component is inside the viewport, using IntersectionObserver API
npm install react-intersection-observer-forkuseInView it's easier than ever to
sh
yarn add react-intersection-observer
`
or NPM:
`sh
npm install react-intersection-observer --save
`
Usage
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#### useInView
`js
// Use object destructing, so you don't need to remember the exact order
const { ref, inView, entry } = useInView(options);
// Or array destructing, making it easy to customize the field names
const [ref, inView, entry] = useInView(options);
`
React Hooks make it easy to monitor the inView state of your components. Call
the useInView hook with the (optional) options you need. It will
return an array containing a ref, the inView status and the current
entry.
Assign the ref to the DOM element you want to monitor, and the hook will
report the status.
`jsx
import React from 'react';
import { useInView } from 'react-intersection-observer';
const Component = () => {
const { ref, inView, entry } = useInView({
/ Optional options /
threshold: 0,
});
return (
{Header inside viewport ${inView}.}
);
};
`
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To use the component, you pass it a function. It will be called
whenever the state changes, with the new value of inView. In addition to the
inView prop, children also receive a ref that should be set on the
containing DOM element. This is the element that the IntersectionObserver will
monitor.
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 { InView } from 'react-intersection-observer';
const Component = () => (
{({ inView, ref, entry }) => (
{Header inside viewport ${inView}.}
)}
);
export default Component;
`
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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 to will be
passed to the HTML element, allowing you set the className, style, etc.
`jsx
import { InView } from 'react-intersection-observer';
const Component = () => (
console.log('Inview:', inView)}>
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.
API
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Provide these as props on the component or as the options
argument for the hooks.
| Name | Type | Default | Required | Description |
| ---------------------- | ---------------------- | --------- | -------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| root | Element | document | false | The IntersectionObserver interface's read-only root property identifies the Element or Document whose bounds are treated as the bounding box of the viewport for the element which is the observer's target. If the root is null, then the bounds of the actual document viewport are used. |
| 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 \| number[] | 0 | false | Number between 0 and 1 indicating the percentage that should be visible before triggering. Can also be an array of numbers, to create multiple trigger points. |
| trackVisibility 🧪 | boolean | false | false | A boolean indicating whether this IntersectionObserver will track changes in a target’s visibility. |
| delay 🧪 | number | undefined | false | A number indicating the minimum delay in milliseconds between notifications from this observer for a given target. This must be set to at least 100 if trackVisibility is true. |
| skip | boolean | false | false | Skip creating the IntersectionObserver. You can use this to enable and disable the observer as needed. If skip is set while inView, the current state will still be kept. |
| triggerOnce | boolean | false | false | Only trigger the observer once. |
| initialInView | boolean | false | false | Set the initial value of the inView boolean. This can be used if you expect the element to be in the viewport to start with, and you want to trigger something when it leaves. |
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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, inView, entry}) => React.ReactNode, ReactNode | | true | Children expects a function that receives an object containing the inView 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. |
(inView, entry) => void | | false | Call this function whenever the in view state changes. It will receive the inView boolean, alongside the current IntersectionObserverEntry. |
trackVisibility and delay options.
entry back, you can then monitor if isVisible is true.
jsx
const TrackVisible = () => {
const { ref, entry } = useInView({ trackVisibility: true, delay: 100 });
return {entry?.isVisible};
};
`
This is still a very new addition, so check
caniuse for current browser
support. If trackVisibility has been set, and the current browser doesn't
support it, a fallback has been added to always report isVisible as true.
It's not added to the TypeScript lib.d.ts file yet, so you will also have to
extend the IntersectionObserverEntry with the isVisible boolean.
Recipes
The IntersectionObserver itself is just a simple but powerful tool. Here's a
few ideas for how you can use it.
- Lazy image load
- Trigger animations
- Track impressions _(Google Analytics, Tag
Manager, etc)_
FAQ
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You can wrap multiple ref assignments in a single useCallback:
`jsx
import React, { useRef } from 'react';
import { useInView } from 'react-intersection-observer';
function Component(props) {
const ref = useRef();
const [inViewRef, inView] = useInView();
// Use useCallback so we don't recreate the function on each render - Could result in infinite loop
const setRefs = useCallback(
(node) => {
// Ref's from useRef needs to have the node assigned to current
ref.current = node;
// Callback refs, like the one from useInView, is a function that takes the node as an argument
inViewRef(node);
},
[inViewRef],
);
return Shared ref is visible: {inView};
}
`
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When using rootMargin, the margin gets added to the current root - If your
application is running inside a