[英]Component is undefined when use react-bootstrap
I have code for react-bootstrap like this.我有这样的 react-bootstrap 代码。
import React from 'react'
import { Link } from 'react-router-dom'
import { Navbar, NavbarBrand, NavItem, Nav } from 'react-bootstrap'
import './App.css'
import NavbarToggle from 'react-bootstrap/esm/NavbarToggle'
import Routes from './Routes'
import NavbarCollapse from 'react-bootstrap/esm/NavbarCollapse'
import { LinkContainer } from 'react-router-bootstrap'
function App() {
return (
<div className="App container">
<Navbar fluid collapseOnSelect>
<Navbar.Header>
<NavbarBrand>
<Link to="/">Scratch</Link>
</NavbarBrand>
<NavbarToggle />
</Navbar.Header>
<NavbarCollapse>
<Nav pullRight>
<LinkContainer to="/signup">
<NavItem>Signup</NavItem>
</LinkContainer>
<LinkContainer to="/login">
<NavItem>Sign</NavItem>
</LinkContainer>
</Nav>
</NavbarCollapse>
</Navbar>
<Routes />
</div>
)
}
export default App
it occurred errors.它发生错误。 The errors message are
错误消息是
Error: Element type is invalid: expected a string (for built-in components) or a class/function (for composite components) but got: undefined.错误:元素类型无效:应为字符串(对于内置组件)或类/函数(对于复合组件)但得到:未定义。 You likely forgot to export your component from the file it's defined in, or you might have mixed up default and named imports.
您可能忘记从定义组件的文件中导出组件,或者您可能混淆了默认导入和命名导入。
Note: when I omitted Navbar.Header
it worked correctly.注意:当我省略
Navbar.Header
它工作正常。
NavBar.Header
was removed in release v1 of React-bootstrap. NavBar.Header
在React-bootstrap 的v1 版本中被移除。 Basically, if you add this component, it primarily adds to the DOM a div
with a class of navbar-header
.基本上,如果你添加这个组件,它主要是向 DOM 添加一个带有
navbar-header
类的div
。
<div class="navbar-header"></div>
If you are curious to know or want to replicate its behavior, you can take a look at this answer: What does "navbar-header" class do in Bootstrap?如果您很想知道或想复制它的行为,可以看看这个答案: Bootstrap 中的“navbar-header”类做了什么? or take a look at some outdated Bootstrap stylesheet (prior to v4).
或查看一些过时的 Bootstrap 样式表(v4 之前)。
If you have the leisure of updating your layout, take a look at the updated examples of React-bootstrap Nav here: https://react-bootstrap.github.io/components/navbar/#navbars如果你有空闲更新你的布局,看看这里 React-bootstrap Nav 的更新示例: https : //react-bootstrap.github.io/components/navbar/#navbars
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