text: import React, { useState,useReducer } from 'react'
  // useReducer介绍和简单使用
  function Example4(){
    const [count,setCount] = useState(0)
    return (
      <div>
        <p>You clicked {count} times</p>
        <button onClick={()=>{setCount(count+5  )}}>click me</button>   
      </div>
    )
  }
  export default Example4
  