好客租房42-react组件基础综合案例-渲染列表无数据并优化

class HelloWorld extends React.Component {
     //初始化状态
     state={
         // comments:[{
         //     id:1,name:"geyao",content:"哈哈"
         // },{
         //     id:2,name:"fangfang",content:"哈哈"
         // },{
         //     id:3,name:"geyao",content:"哈哈"
         // }]
         comments:[]
     }
     render() {
         return (
             <div className="app">
                 <div>
                     <input
                         className="user"
                         type="text"
                         placeholder="请输入评论人"
                     />
                     <br />
                     <textarea
                         className="content"
                         cols="30"
                         rows="10"
                         placeholder="请输入评论列表"
                     ></textarea>
                     <br />
                     <button>发表评论</button>
                 </div>
                 {this.state.comments.length===0?(
                         <div className="no-comment">暂无评论,快去评论吧~</div>
                 ):(
                     <ul>
                     {/* <li>
                         <h3>评论人:jack</h3>
                         <h3>评论内容:沙发</h3>
                     </li> */}
                     {this.state.comments.map(item=>(
                         <li key={item.key}>
                         <h3>评论人:{item.name}</h3>
                         <p>评论内容:{item.content}</p>
                     </li>
                     )
                     )}
                 </ul>
                 )}
             </div>
         )
     }
 }
 ReactDOM.render(<HelloWorld />, document.getElementById('root'))