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import React, { useEffect, useMemo, useRef, useState } from "react"; |
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|
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/** |
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* Props for InView component. |
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*/ |
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interface InViewProps { |
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children: React.ReactNode; |
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viewRatio?: number; |
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classNames?: string[]; |
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} |
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|
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/** |
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* Component to render children when they are in view. |
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* |
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* @param props Component props. |
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* @param props.children Component to render when in view. |
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* @param [props.viewRatio=0.1] Ratio of the element that needs to be in view to trigger the render. (1.0 being fully in view) |
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* |
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* @param [props.classNames=[]] Additional class names to apply to the wrapper. |
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* @class |
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*/ |
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const InView: React.FC<InViewProps> = ({ |
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children, |
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viewRatio = 0.1, |
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classNames = [], |
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}) => { |
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const [isInView, setIsInView] = useState(false); |
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|
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const wrapperRef = useRef(null); |
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|
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// Component observer initialization. |
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const observer = useMemo( |
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() => |
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new IntersectionObserver( |
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([entry]) => { |
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const { isIntersecting } = entry; |
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|
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// only update state if element is in view |
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if (isIntersecting) { |
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setIsInView(isIntersecting); |
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} |
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}, |
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{ threshold: viewRatio } |
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), |
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[viewRatio] |
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); |
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|
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// Class list for the wrapper. |
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const classList = useMemo( |
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() => ["tableberg-in-view-wrapper", ...classNames].join(" "), |
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[classNames] |
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); |
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|
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useEffect(() => { |
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if (wrapperRef.current) { |
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observer.observe(wrapperRef.current); |
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} |
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}, [observer, wrapperRef]); |
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|
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// disconnect observer when component is in view to prevent multiple calls |
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useEffect(() => { |
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if (isInView) { |
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observer.disconnect(); |
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} |
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}, [observer, isInView]); |
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|
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return ( |
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<div className={classList} ref={wrapperRef}> |
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{isInView && children} |
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</div> |
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); |
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}; |
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|
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export default InView; |
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|
