react hooks useReducer

import React, { useReducer } from 'react';

function ReducerDemo(){
    const [ count , dispatch] =useReducer((state,action)=>{
        //判断action类型
        switch(action){
            case 'add':
                return state+1
            case 'sub':
                return state-1
            default:
                return state
        }
    },0)  //当前count

    return(
        <div>
            <h2>现在的数字是{count}</h2>
            <button onClick={()=>dispatch('add')}>加</button>
            <button onClick={()=>dispatch('sub')}>减</button>
        </div>
    )
}

export default ReducerDemo