/** * Copyright (c) Meta Platforms, Inc. and affiliates. * * This source code is licensed under the MIT license found in the * LICENSE file in the root directory of this source tree. * * @flow strict-local * @format * @oncall react_native */ 'use strict'; import type {ItemDataType} from '../components/itemData'; import {LIST_1000_ITEMS} from '../components/itemData'; import ItemList from '../components/ItemList'; import * as React from 'react'; const {useState, useEffect} = React; const ItemListMemo = React.memo(ItemList); function BadExample(props: {listData: ItemDataType[], filteredText: string}) { const {listData, filteredText} = props; const [visibleListData, setVisibleListData] = useState(listData); useEffect(() => { setVisibleListData( listData.filter(item => item.name.toUpperCase().includes(filteredText.toUpperCase()), ), ); }, [listData, filteredText]); return ; } function GoodExample(props: {listData: ItemDataType[], filteredText: string}) { const {listData, filteredText} = props; const visibleListData = listData.filter(item => item.name.toUpperCase().includes(filteredText.toUpperCase()), ); return ; } function SetStateInWrongEffectBadExample(): React.Node { return ; } function SetStateInWrongEffectGoodExample(): React.Node { return ; } export default { title: 'Re-render with unnecessary effect and state changes', description: 'You may not need an effect in your component. State updates in unnecessary effects will trigger re-render that can be avoided.', Bad: SetStateInWrongEffectBadExample, Good: SetStateInWrongEffectGoodExample, };