Intersection Observer Hooks
These hooks help you track when an element enters or leaves the viewport.

Table of Contents

useInView

This hook just wraps the react-intersection-observer library which uses internally the IntersectionObserver API. As some old browsers don't support it, useInView also returns a supported prop indicating if it's supported or not.

Usage

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import useInView from "@frontity/hooks/use-in-view";
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​
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const MyLazyElement = ({ children }) => {
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// Get the reference and the visibility status.
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const { ref, inView } = useInView({ triggerOnce: true });
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​
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// Pass the reference to the container and render `children` if
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// the container is visible, or a placeholder otherwise.
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return <div ref={ref}>{inView ? children : <MyPlaceholder />}</div>;
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};
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Parameters

It accepts a single object with the following props:
Name
Type
Default
Required
Description
root
Element
window
no
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"
no
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 or array of numbers
0
no
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.
triggerOnce
boolean
false
no
Only trigger this method once

Return value

An object with the following properties:
Name
Type
Description
ref
React.RefObject
React reference object pointing to the DOM element. It must be passed to the element you want to track.
inView
boolean
Boolean indicating if the element is visible. The value is always true if supported is false.
supported
boolean
Boolean indicating if IntersectionObserver is supported by the browser.

Demo

This example project shows how to use the Intersection Observer Hook useInView available in the @frontity/hooks package or directly implemented in some components available at @frontity/components.