# Getting Started with Create React App
This project was bootstrapped with [Create React App](https://github.com/facebook/create-react-app).
## Available Scripts
In the project directory, you can run:
### `npm start`
Runs the app in the development mode.\
Open [http://localhost:3000](http://localhost:3000) to view it in your browser.
The page will reload when you make changes.\
You may also see any lint errors in the console.
### `npm test`
Launches the test runner in the interactive watch mode.\
See the section about [running tests](https://facebook.github.io/create-react-app/docs/running-tests) for more information.
### `npm run build`
Builds the app for production to the `build` folder.\
It correctly bundles React in production mode and optimizes the build for the best performance.
The build is minified and the filenames include the hashes.\
Your app is ready to be deployed!
See the section about [deployment](https://facebook.github.io/create-react-app/docs/deployment) for more information.
### `npm run eject`
**Note: this is a one-way operation. Once you `eject`, you can't go back!**
If you aren't satisfied with the build tool and configuration choices, you can `eject` at any time. This command will remove the single build dependency from your project.
Instead, it will copy all the configuration files and the transitive dependencies (webpack, Babel, ESLint, etc) right into your project so you have full control over them. All of the commands except `eject` will still work, but they will point to the copied scripts so you can tweak them. At this point you're on your own.
You don't have to ever use `eject`. The curated feature set is suitable for small and middle deployments, and you shouldn't feel obligated to use this feature. However we understand that this tool wouldn't be useful if you couldn't customize it when you are ready for it.
## Learn More
You can learn more in the [Create React App documentation](https://facebook.github.io/create-react-app/docs/getting-started).
To learn React, check out the [React documentation](https://reactjs.org/).
### Code Splitting
This section has moved here: [https://facebook.github.io/create-react-app/docs/code-splitting](https://facebook.github.io/create-react-app/docs/code-splitting)
### Analyzing the Bundle Size
This section has moved here: [https://facebook.github.io/create-react-app/docs/analyzing-the-bundle-size](https://facebook.github.io/create-react-app/docs/analyzing-the-bundle-size)
### Making a Progressive Web App
This section has moved here: [https://facebook.github.io/create-react-app/docs/making-a-progressive-web-app](https://facebook.github.io/create-react-app/docs/making-a-progressive-web-app)
### Advanced Configuration
This section has moved here: [https://facebook.github.io/create-react-app/docs/advanced-configuration](https://facebook.github.io/create-react-app/docs/advanced-configuration)
### Deployment
This section has moved here: [https://facebook.github.io/create-react-app/docs/deployment](https://facebook.github.io/create-react-app/docs/deployment)
### `npm run build` fails to minify
This section has moved here: [https://facebook.github.io/create-react-app/docs/troubleshooting#npm-run-build-fails-to-minify](https://facebook.github.io/create-react-app/docs/troubleshooting#npm-run-build-fails-to-minify)
React function
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更新于2023-09-07
收藏 448KB ZIP 举报
React Function是React.js库中的一种组件定义方式,它是React 16.8版本引入的 Hooks 特性的一部分,用于替代经典的React Class组件。在React应用中,函数组件扮演着核心角色,因为它们允许开发者以更简洁、易于理解和维护的方式编写UI逻辑。
函数组件的基本形式是一个JavaScript函数,它接收一个名为`props`的对象作为参数,并返回React元素。React元素描述了屏幕上的UI应该看起来如何。例如,一个简单的函数组件可能如下所示:
```jsx
function Welcome(props) {
return <h1>Hello, {props.name}</h1>;
}
```
在上述代码中,`Welcome`函数是一个React组件,它接收一个`props`对象,并根据`props.name`返回一个`<h1>`元素。这种编写方式使得组件更易于理解和测试,因为它不涉及类、实例方法或生命周期钩子。
React Hooks 是与函数组件一起使用的API,允许我们在不编写类的情况下使用状态(state)和其他React特性。其中最常用的Hooks包括`useState`(用于管理状态)和`useEffect`(用于处理副作用)。
`useState` Hook 允许函数组件拥有自己的状态。例如,我们可以在组件中添加一个计数器:
```jsx
import React, { useState } from 'react';
function Counter() {
const [count, setCount] = useState(0);
function increment() {
setCount(count + 1);
}
return (
<div>
<p>Count: {count}</p>
<button onClick={increment}>Increment</button>
</div>
);
}
```
在这个例子中,`useState`返回一对值:当前状态`count`和一个用于更新状态的函数`setCount`。当点击按钮时,`increment`函数被调用,`setCount`更新状态,导致组件重新渲染。
`useEffect` Hook 则用于在函数组件中执行副作用操作,如数据获取、订阅、手动更改DOM等。副作用通常应在组件渲染后或渲染前进行。`useEffect`接受两个参数:一个函数(副作用函数)和一个依赖数组。如果依赖数组为空,副作用会在每次组件渲染时运行;如果有依赖项,只有当依赖项改变时才会执行。
```jsx
import React, { useState, useEffect } from 'react';
function Example() {
const [count, setCount] = useState(0);
useEffect(() => {
document.title = `You clicked ${count} times`;
}, [count]); // 只有当count变化时,才会重新设置文档标题
return (
<div>
<p>You clicked {count} times</p>
<button onClick={() => setCount(count + 1)}>
Click me
</button>
</div>
);
}
```
函数组件结合Hooks极大地简化了React应用的架构,使得代码更易于理解和维护。React Fun这个主题涵盖的内容非常广泛,包括但不限于组件化、Props、State、生命周期、事件处理、条件渲染、错误边界、性能优化等方面。通过深入学习和实践React Function,开发者可以更好地利用React构建高效、可复用的用户界面。

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