我得到这个错误:
Uncaught Error: Invariant Violation: Element type is invalid: expected a string (for built-in components) or a class/function (for composite components) but got: object.
这是我的代码:
var React = require('react')
var ReactDOM = require('react-dom')
var Router = require('react-router')
var Route = Router.Route
var Link = Router.Link
var App = React.createClass({
render() {
return (
<div>
<h1>App</h1>
<ul>
<li><Link to="/about">About</Link></li>
</ul>
</div>
)
}
})
var About = require('./components/Home')
ReactDOM.render((
<Router>
<Route path="/" component={App}>
<Route path="about" component={About} />
</Route>
</Router>
), document.body)
我的家。jsx文件:
var React = require('react');
var RaisedButton = require('material-ui/lib/raised-button');
var Home = React.createClass({
render:function() {
return (
<RaisedButton label="Default" />
);
},
});
module.exports = Home;
除了进口/出口问题提到。我发现使用React.cloneElement()向子元素添加道具，然后渲染它给了我同样的错误。
我不得不改变:
render() {
const ChildWithProps = React.cloneElement(
this.props.children,
{ className: `${PREFIX}-anchor` }
);
return (
<div>
<ChildWithProps />
...
</div>
);
}
to:
render() {
...
return (
<div>
<ChildWithProps.type {...ChildWithProps.props} />
</div>
);
}
有关更多信息，请参阅React.cloneElement()文档。
就我而言，
//details.js
import React from 'react'
const Details = (props) =>{
return <h1>Details</h1>
}
export default Details;
//main.js
import React from "react";
import { withRouter } from "react-router";
import {Route,BrowserRouter as Router,Redirect,Switch,Link} from "react-router-dom";
import Details from "./myAccount/details";
const Main = (props) => {
return (
<>
<Switch>
<Route path="/my-account/details" component={<Details />} />
</Switch>
</>
);
};
export default withRouter(Main);
===========================
Replaced with below one, error got fixed
component={<Details />} with component={Details}
我发现了这个错误的另一个原因。它与CSS-in-JS向React组件中返回函数的顶层JSX返回空值有关。
例如:
const Css = styled.div`
<whatever css>
`;
export function exampleFunction(args1) {
...
return null;
}
export default class ExampleComponent extends Component {
...
render() {
const CssInJs = exampleFunction(args1);
...
return (
<CssInJs>
<OtherCssInJs />
...
</CssInJs>
);
}
我会得到这样的警告:
警告:反应。createElement: type无效——期望一个字符串(对于内置组件)或一个类/函数(对于复合组件)，但得到:null。
接着是这个错误:
未捕获错误:元素类型无效:期望为字符串(对于内置组件)或类/函数(对于复合组件)，但得到:null。
我发现这是因为我试图渲染的CSS-in- js组件没有CSS。我通过确保有CSS被返回而不是一个空值来修复它。
例如:
const Css = styled.div`
<whatever css>
`;
export function exampleFunction(args1) {
...
return Css;
}
export default class ExampleComponent extends Component {
...
render() {
const CssInJs = exampleFunction(args1);
...
return (
<CssInJs>
<OtherCssInJs />
...
</CssInJs>
);
}
