一、概念

把一个组件当成另外一个组件的参数传入，然后通过一定的判断，返回新的组件。

二、基本用法

三、实战

例1：监听鼠标位置

App.js

import React from 'react'
import HOCDemo from './6.高级特性/4.HOCDemo'

function App() {
  return (
    <div>
      <HOCDemo a='999' />
    </div>
  )
}

export default App

4.HOCDemo.js

import React from 'react'

// 高阶组件
const withMouse = (Component) => {
  class withMouseComponent extends React.Component {
    constructor(props) {
      super(props)
      this.state = { x: 0, y: 0 }
    }

    handleMouseMove = (event) => {
      this.setState({
        x: event.clientX,
        y: event.clientY
      })
    }

    render() {
      return (
        <div style={{ height: '500px', background: 'pink' }} onMouseMove={this.handleMouseMove}>
          {/* 1. 透传所有 props (vue使用$props v-bind) 2. 增加 mouse 属性 */}
          <Component {...this.props} mouse={this.state}/>
        </div>
      )
    }
  }
  return withMouseComponent
}

const App = (props) => {
  const a = props.a // 999
  const { x, y } = props.mouse // 接收 mouse 属性
  return (
    <div style={{ height: '500px' }}>
      <h1>The mouse position is ({x}, {y})</h1>
      <p>{a}</p>
    </div>
  )
}

export default withMouse(App) // 返回高阶函数

例2：路由鉴权

App.js

// 导入路由
import { unstable_HistoryRouter as HistoryRouter, Routes, Route } from 'react-router-dom'
import { history } from './utils/history'
import './App.css'

import AuthRoute from './components/AuthRoute'

// 导入页面组件
// import Login from './pages/Login'
// import SysLayout from '@/pages/Layout'
// import Home from './pages/Home'
// import Article from './pages/Article'
// import Publish from './pages/Publish'

// 导入必要组件
import { lazy, Suspense } from 'react'
// 按需导入路由组件
const Login = lazy(() => import('./pages/Login'))
const SysLayout = lazy(() => import('@/pages/Layout'))
const Home = lazy(() => import('./pages/Home'))
const Article = lazy(() => import('./pages/Article'))
const Publish = lazy(() => import('./pages/Publish'))

// 配置路由规则
function App() {
  return (
    <HistoryRouter history={history}>
      <Suspense
        fallback={
          <div
            style={{
              textAlign: 'center',
              marginTop: 200
            }}
          >
            loading...
          </div>
        }
      >
        <div className="App">
          <Routes>
            {/* 需要鉴权的路由 */}
            <Route
              path="/"
              element={
                <AuthRoute>     // 高阶组件在这！！！！！！
                  <SysLayout/>
                </AuthRoute>
              }
            >
              <Route index element={<Home />}/>
              <Route path="/article" element={<Article />} />
              <Route path="/publish" element={<Publish />} />
            </Route>

            {/* 不需要鉴权的路由 */}
            <Route path="/login" element={<Login/>} />
          </Routes>
        </div>
      </Suspense>
    </HistoryRouter>
  )
}

export default App;

AuthRoute.js

// 1. 判断token是否存在
// 2. 如果存在 直接正常渲染
// 3. 如果不存在 重定向到登录路由

// 高阶组件: 把一个组件当成另外一个组件的参数传入 然后通过一定的判断 返回新的组件
import { getToken } from '@/utils'
import { Navigate } from 'react-router-dom'

function AuthRoute ({ children }) {
  const isToken = getToken()
  if (isToken) {
    return <>{children}</>
  } else {
    return <Navigate to="/login" replace />
  }
}

export default AuthRoute

// <AuthComponent> <Layout/> </AuthComponent>
// 登录：<><Layout/></>
// 非登录：<Navigate to="/login" replace />

具体请看我的项目
项目地址

四、Vue如何实现高阶组件？？？