const CartPage = () => { const [cart, setCart] = useCart() <-- The value returning an empty array on first mount } 我试图用本地存储值而不是空数组来装载cart的值。为什么cart在其他组件页上返回一个空数组,即使我已经使用useEffect来设置值。如何让cart在本地存储中返回值,而不是在第一次装载...
function instantiateReactComponent(node, shouldHaveDebugID) { var instance; if (node === null || node === false) { instance = ReactEmptyComponent.create(instantiateReactComponent); } else if (typeof node === 'object') { var element = node; // Special case string values if (typeof el...
import React, { useState, useEffect } from 'react'; import ItemBox from '@/components/ItemBox/ItemBox'; // @ts-ignore import Arrow from '@/assets/h5/arrow.png'; import styles from './index.less' export default function(props){ const [state, setState] = useState(Array(3).fill(1))...
import{useState,useEffect}from"react";importReactDOMfrom"react-dom/client";functionTimer(){const[count,setCount]=useState(0);useEffect(()=>{setTimeout(()=>{setCount((count)=>count+1);},1000);},[]);// <- add empty brackets herereturnI've rendered{count}times!;}constroot=ReactDOM....
push-to-state-array.png 添加元素 这里我们使用useState钩子来管理state数组。注意,我们给setState传递了一个函数,因为函数会保证以当前(最新的)状态调用。 代码语言:javascript 代码运行次数:0 运行 AI代码解释 setNames(current=>[...current,'Carl']); ...
const [array, setArray] = useState(["X"]); const removeValue = () => { setArray((current) => { return current.filter((item) => item !== array[0]); }); console.log("array", array); //It still refers to the old value. ...
import React, { useState } from 'react'; import ReactQuill from 'react-quill'; import 'react-quill/dist/quill.snow.css'; function MyComponent() { const [value, setValue] = useState(''); return <ReactQuill theme="snow" value={value} onChange={setValue} />; }...
The firstReact.useEffect hookhas an empty array. Since there are no dependencies, it only gets triggered once. But in the secondReact.useEffect hook, I added my statevariableas a dependency. Any time my statevariable,counter, changes in value, then the secondReact.useEffectfunction will re-act...
useState<Selection>(new Set([2])); return ( <Table aria-label="Table with controlled selection" selectionMode="multiple" selectedKeys={selectedKeys} onSelectionChange={setSelectedKeys} {...props} > <TableHeader columns={columns}> {(column) => ( <Column key={column.uid}> {column.name} </...
components/Book.js create mode 100644 src/components/BookForm.js create mode 100644 src/components/BooksList.js create mode 100644 src/components/EditBook.js create mode 100644 src/components/Header.js create mode 100644 src/context/BooksContext.js create mode 100644 src/hooks/useLocalStorage.js ...