react怎么循环map

<ul id="ul_rwardList">

    {

        this.state.reward.map(function (item) {

            return (

                <li className="db vh" key={item.id}>

                    <div className="fx1">{item.num}</div>

                    <div className="fx1">{item.username}</div>

                    <div className="fx1 text-right">{item.rward_time}</div>

                </li>

            )})

    }

</ul>