重渲染

React 的渲染机制是深度优先。

import * as React from 'react'
import { useState, useEffect} from 'react'
import { createRoot } from 'react-dom/client'

function A() {
  console.log('A')
  return <B/>
}

function B() {
  console.log('B')
  return <C/>
}

function C() {
  console.log('C')
  return null
}

function D() {
  console.log('D')
  return null
}

function App() {
  const [state, setState] = useState(0)
  useEffect(() => {
    setState(state => state + 1)
  }, [])
  console.log('App')
  return (
    <div>
      <A state={state}/>
      <D/>
    </div>
  )
}

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