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ばかでか配列とかをバーチャルスクロールで表示するコンポーネント
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| import { useState, useDeferredValue } from 'react' | |
| type Props<T> = { | |
| height: number | |
| items: T[] | |
| maxItemCount?: number | |
| itemHeight: number | |
| bufferCount?: number | |
| renderItem: (item: T, index: number) => JSX.Element | |
| onRender?: (lastIndex: number) => void | |
| } | |
| export function ItemListInVirtualScroll<T>({ | |
| items, | |
| maxItemCount = items.length, | |
| height, | |
| itemHeight, | |
| bufferCount = 3, | |
| renderItem, | |
| onRender, | |
| }: Props<T>) { | |
| const [scrollY, setScrollY] = useState(0) | |
| const startIndex = useDeferredValue( | |
| Math.max(Math.floor(scrollY / itemHeight) - bufferCount, 0) | |
| ) | |
| const lastIndex = Math.min( | |
| startIndex + Math.ceil(height / itemHeight) + bufferCount * 2, | |
| maxItemCount - 1 | |
| ) | |
| if (onRender) { | |
| onRender(lastIndex) | |
| } | |
| return ( | |
| <div | |
| style={{ | |
| height: `${height}px`, | |
| overflowY: 'scroll', | |
| }} | |
| onScroll={(e) => { | |
| setScrollY(e.currentTarget.scrollTop) | |
| }} | |
| > | |
| <div style={{ height: `${itemHeight * maxItemCount - height}px` }}> | |
| <div | |
| style={{ | |
| translate: `0px ${startIndex * itemHeight}px`, | |
| }} | |
| > | |
| {items | |
| .slice(startIndex, lastIndex) | |
| .map((item, index) => renderItem(item, startIndex + index))} | |
| </div> | |
| </div> | |
| </div> | |
| ) | |
| } |
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