学习React 遇到的报错记录

学习React时遇到的报错记录

1._registerComponent(…): Target container is not a DOM element.
错误原因:在页面中找不到对应的DOM元素,
错误代码:

<div id="app">div>   //此处的DOM元素的ID是app
body>
<script type="text/babel">
    function MailBox(props) {
        const unreadMessage = props.unreadMessage;
        return(
            <div>
                <h1>Hello!h1>
                {unreadMessage.length > 0 &&
                <h2>
                    You have {unreadMessage.length} unread messages.
                h2>
                }
            div>
        )
    }
    const message=['React','hello','cheng','hahah'];
    ReactDOM.render(
        <MailBox unreadMessage={message}/>,
        document.getElementById('root')   //此处却在查找ID为root的DOM元素进行渲染,页面中没有对应的元素,因此报错
    )
script>