Javascript Reactjs：警告：React.createElement：类型不应为空或未定义
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Reactjs: Warning: React.createElement: type should not be null or undefined
提问by Non
this the full error
这是完整的错误
Warning: React.createElement: type should not be null or undefined. It should be a string (for DOM elements) or a ReactClass (for composite components).
警告：React.createElement：类型不应为空或未定义。它应该是一个字符串（对于 DOM 元素）或一个 ReactClass（对于复合组件）。
and this is all I have in this view
这就是我在这个观点中的全部
import React, { Component } from 'react';
import Router, {Link, RouteHandler} from 'react-router';
import { Grid, Row, Column, List, ListItem } from '../../components/Layout';
import { RaisedButton, Paper } from 'material-ui';
const videosInformation = {
time : 25,
gameId : 15665,
date : '12 10 2015',
gameName : "Black Hyman"
};
export default class Home extends Component {
static contextTypes = {
router : React.PropTypes.func
}
render () {
return <Grid>
<Row>
<Column>
<Paper>
<List subheader="Player Info">
<ListItem primaryText={`Name: ${videosInformation.time}`} />
<ListItem primaryText={`Nickname: ${videosInformation.date}`} />
<ListItem primaryText={`Age: ${videosInformation.gameId}`} />
<ListItem primaryText={`Language: ${videosInformation.gameName}`} />
</List>
</Paper>
</Column>
<Column>
<iframe width="560" height="315" src="https://www.youtube.com/embed/Ta4xuThmAsQ" frameBorder="0" allowFullScreen></iframe>
</Column>
</Row>
</Grid>;
};
}
I am using Material-UI
我正在使用Material-UI
采纳答案by Ed Ballot
It is likely that your Layoutfile is not exporting one of the variables from this line
您的Layout文件很可能没有从这一行导出变量之一
import { Grid, Row, Column, List, ListItem } from '../../components/Layout';
The warning would happen if one of those is undefined.
如果其中之一未定义，则会发生警告。
回答by pjehan
I know the right solution has been found here but I just wanted to share another possible reason for the ReactJS React.createElement: type should not be null or undefinedwarning to trigger.
我知道在这里找到了正确的解决方案，但我只是想分享React.createElement: type should not be null or undefined触发ReactJS警告的另一个可能原因。
It can also happens when you have a circular dependency in your modules. Then, doing a console.log()of your imported module would return an empty object.
当您的模块中有循环依赖时，也会发生这种情况。然后，执行console.log()导入模块的操作将返回一个空对象。
For further details, have a look at this other stackoverflow thread: Require returns an empty object
有关更多详细信息，请查看另一个 stackoverflow 线程：Require returns an empty object
回答by Michael McAlpin
Just in case anyone has run into this issue and the above solutions are not helping, all I had to do was move my top-level ReactDOM.render() function below the rest of the JavaScript to ensure all variables were initialized before being called. I was following the tutorial at https://reactjs.net/getting-started/tutorial_aspnet4.html
以防万一有人遇到这个问题并且上述解决方案没有帮助，我所要做的就是将我的顶级 ReactDOM.render() 函数移到 JavaScript 的其余部分下方，以确保所有变量在调用之前都已初始化。我正在关注https://reactjs.net/getting-started/tutorial_aspnet4.html 上的教程
