无需导入React就可以使用JSX [英] JSX can be used without importing React

问题描述

我正在尝试使用版本4.0.0的create-react-app运行我的第一个React JSX文件，它可以工作！但是，我的JSX中没有React的import语句，它也可以工作，但是很奇怪.该项目是通过 create-react-app 命令创建的，版本为4.0.0.

I'm trying to run my first React JSX file with create-react-app with version 4.0.0 and it works! However, I don't have the import statements of React included in my JSX and it works too but it is very weird. The project is created by create-react-app command with version 4.0.0.

App.js文件:

/*不导入React，但也可以！ */

/* without import React but works too! */

 import { Component } from "react";
class App extends Component {
  render() {
    return <div>456</div>;
  }
}
export default App;

推荐答案

This is new with the JSX transform introduced with React 17 :

与React 17版本一起，我们希望做出一些 JSX转换的改进，但我们不想破坏 现有设置.这就是为什么我们与Babel合作，提供新的， JSX转换的改版 升级.

Together with the React 17 release, we’ve wanted to make a few improvements to the JSX transform, but we didn’t want to break existing setups. This is why we worked with Babel to offer a new, rewritten version of the JSX transform for people who would like to upgrade.

完全可以选择升级到新的转换，但是它具有一个 一些好处:

Upgrading to the new transform is completely optional, but it has a few benefits:

• 通过新的转换，您可以使用JSX而不导入React .
• 根据您的设置，其编译后的输出可能会稍微改善包的大小.
• 它将实现未来的改进，从而减少学习React所需的概念.

• With the new transform, you can use JSX without importing React.
• Depending on your setup, its compiled output may slightly improve the bundle size.
• It will enable future improvements that reduce the number of concepts you need to learn React.

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