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Prevent parent from unnecessary updates when scrolling window. #47

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Merged
merged 1 commit into from
Aug 13, 2020
Merged

Prevent parent from unnecessary updates when scrolling window. #47

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18 changes: 15 additions & 3 deletions src/useRect.js
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ import useIsomorphicLayoutEffect from './useIsomorphicLayoutEffect'

export default function useRect(nodeRef) {
const [element, setElement] = React.useState(nodeRef.current)
const [rect, setRect] = React.useState(null)
const [rect, dispatch] = React.useReducer(rectReducer, null);
const initialRectSet = React.useRef(false)

useIsomorphicLayoutEffect(() => {
Expand All @@ -18,7 +18,8 @@ export default function useRect(nodeRef) {
useIsomorphicLayoutEffect(() => {
if (element && !initialRectSet.current) {
initialRectSet.current = true
setRect(element.getBoundingClientRect())
const rect = element.getBoundingClientRect();
dispatch({ rect });
}
}, [element])

Expand All @@ -27,7 +28,9 @@ export default function useRect(nodeRef) {
return
}

const observer = observeRect(element, setRect)
const observer = observeRect(element, rect => {
dispatch({ rect });
});

observer.observe()

Expand All @@ -38,3 +41,12 @@ export default function useRect(nodeRef) {

return rect
}

function rectReducer(state, action) {
const rect = action.rect;
if (!state || state.height !== rect.height || state.width !== rect.width) {
return rect;
}
return state;
}