useReducer

1.如何使用useReducer

const reducer =(state = 0, {type})=>{
    switch (type) {
        case "add":
            return state+1
        case 'delete':
            return state-1
        default:
            return state;
    }
}

const Hook =()=>{
    const [count, dispatch] = useReducer(reducer, 0)
    return(
        <div>
           count:{count}
           <button onClick={()=> dispatch({type:'add'})}>add</button>
            <button onClick={()=> dispatch({type:'delete'})}>delete</button>
        </div>
    )
}

export default Hook