class BlackBorderContainer extends React.Component {
        render(){
            console.log(this.props.children[0].props); //object
            this.props.children.map((val,i)=>{
                console.log(val);
                return <div key={i} className="black-board">{val.type}</div>
            })
        }
    }
    ReactDOM.render(
        <BlackBorderContainer>
            <div className='name'>My Name：Lucy</div>
            <p className='age'> My Age：<span>12</span></p>
        </BlackBorderContainer>,
        document.getElementById('example')
    )

我2个console打印出来的内容 可以看出有三个对象，那我这里{val.type}为什么还是错误的？
难道说是因为<BlackBorderContainer>组件内部的不对称，一个是div一个是p的缘故？
{className: "name", children: "My Name：Lucy"}
{$$typeof: Symbol(react.element), type: "div", key: null, ref: null, props: {…}, …}
{$$typeof: Symbol(react.element), type: "p", key: null, ref: null, props: {…}, …}
从中可以看出我最后return的时候 val是正确输出的，但是程序会报错
Uncaught Error: BlackBorderContainer.render(): A valid React element (or null) must be returned. You may have returned undefined, an array or some other invalid object.