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React入门

醉东枫 2022-07-01 阅读 23

React Developer Tools.crx下载地址:​​https://pan.baidu.com/s/137XB-alpKdUS9k-5bHekrg​​

React是一个声明式的,高效的,并且灵活的用于构建用户界面的 JavaScript 库。当数据更改时,React 将有效地更新并渲染正确的组件。组件接收参数,称为 ​​props​​​(属性),并通过 ​​render​​​ 方法返回一个显示的视图层次结构。​​render​​ 方法返回您要渲染的内容描述,然后 React 接受该描述并将其渲染到屏幕上。特别是,​​render​​ 返回一个 React 元素,这是一个渲染内容的轻量级描述。大多数 React 开发人员使用一种名为 JSX 的特殊语法,可以更容易地编写这些结构。每个组件都是封装的,因此它可以独立操作,这允许你从简单的组件构建复杂的UI。

jquery的瓶颈:

1) 一个js文件有千把行是很正常的

2) 各种ajax的callback毫无规则的在源文件里面到处乱飞

3) html代码和dom操作也是随性所欲

 

 

1.hello world

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>Hello World</title>
<script src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>
</head>
<body>
<div id="root"></div>
<script type="text/babel">
function formatName(user) {
return user.firstName + ' ' + user.lastName;
}

const user = {
firstName: 'xu',
lastName: 'tongbao'
};

const element = (
<h1>
Hello, {formatName(user)}!
</h1>
);

ReactDOM.render(
element,
document.getElementById('root')
);
</script>
</body>
</html>

 

 

 

2.时钟

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>Hello World</title>
<script src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>
</head>
<body>
<div id="root"></div>
<script type="text/babel">
function tick() {
const element = (
<div>
<h1>Hello, world!</h1>
<h2>It is {new Date().toLocaleTimeString()}.</h2>
</div>
);
ReactDOM.render(
element,
document.getElementById('root')
);
}

setInterval(tick, 1000);
</script>
</body>
</html>

3.组件和属性

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>Hello World</title>
<script src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>
</head>
<body>
<div id="root"></div>
<script type="text/babel">
function Welcome(props) {
return <h1>Hello, {props.name}</h1>;
}

const element = <Welcome name="xutongbao" />;
ReactDOM.render(
element,
document.getElementById('root')
);
</script>
</body>
</html>

4.组件引用组件

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>Hello World</title>
<script src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>
</head>
<body>
<div id="root"></div>
<script type="text/babel">
function Welcome(props) {
return <h1>Hello, {props.name}</h1>;
}

function App() {
return (
<div>
<Welcome name="xutongbao" />
<Welcome name="徐同保" />
<Welcome name="星河" />
</div>
);
}

ReactDOM.render(
<App />,
document.getElementById('root')
);
</script>
</body>
</html>

5.提取组件

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>Hello World</title>
<script src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>
</head>
<body>
<div id="root"></div>
<script type="text/babel">
function formatDate(date) {
return date.toLocaleDateString();
}

function Avatar(props) {
return (
<img className="Avatar"
src={props.user.avatarUrl}
alt={props.user.name} />
);
}

function UserInfo(props) {
return (
<div className="UserInfo">
<Avatar user={props.user} />
<div className="UserInfo-name">
{props.user.name}
</div>
</div>
);
}

function Comment(props) {
return (
<div className="Comment">
<UserInfo user={props.author} />
<div className="Comment-text">
{props.text}
</div>
<div className="Comment-date">
{formatDate(props.date)}
</div>
</div>
);
}

const comment = {
date: new Date(),
text: '希望你能快乐的学习react!',
author: {
name: '徐同保',
avatarUrl: 'http://placekitten.com/g/64/64'
}
};
ReactDOM.render(
<Comment
date={comment.date}
text={comment.text}
author={comment.author} />,
document.getElementById('root')
);
</script>
</body>
</html>

6.使用状态(state)和生命周期做的时钟

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>Hello World</title>
<script src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>
</head>
<body>
<div id="root"></div>
<script type="text/babel">
class Clock extends React.Component {
constructor(props) {
super(props);
this.state = {date: new Date()};
}

componentDidMount() {
this.timerID = setInterval(
() => this.tick(),
1000
);
}

componentWillUnmount() {
clearInterval(this.timerID);
}

tick() {
this.setState({
date: new Date()
});
}

render() {
return (
<div>
<h1>Hello, world!</h1>
<h2>It is {this.state.date.toLocaleTimeString()}.</h2>
</div>
);
}
}

ReactDOM.render(
<Clock />,
document.getElementById('root')
);
</script>
</body>
</html>

7.事件(开关按钮)

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>Hello World</title>
<script src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>
</head>
<body>
<div id="root"></div>
<script type="text/babel">
class Toggle extends React.Component {
constructor(props) {
super(props);
this.state = {isToggleOn: true};

// 这个绑定是必要的,使`this`在回调中起作用
this.handleClick = this.handleClick.bind(this);
}

handleClick() {
this.setState(prevState => ({
isToggleOn: !prevState.isToggleOn
}));
}

render() {
return (
<button onClick={this.handleClick}>
{this.state.isToggleOn ? 'ON' : 'OFF'}
</button>
);
}
}

ReactDOM.render(
<Toggle />,
document.getElementById('root')
);
</script>
</body>
</html>

8.条件渲染(登录和退出)

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>Hello World</title>
<script src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>
</head>
<body>
<div id="root"></div>
<script type="text/babel">
class LoginControl extends React.Component {
constructor(props) {
super(props);
this.handleLoginClick = this.handleLoginClick.bind(this);
this.handleLogoutClick = this.handleLogoutClick.bind(this);
this.state = {isLoggedIn: false};
}

handleLoginClick() {
this.setState({isLoggedIn: true});
}

handleLogoutClick() {
this.setState({isLoggedIn: false});
}

render() {
const isLoggedIn = this.state.isLoggedIn;

let button = null;
if (isLoggedIn) {
button = <LogoutButton onClick={this.handleLogoutClick} />;
} else {
button = <LoginButton onClick={this.handleLoginClick} />;
}

return (
<div>
<Greeting isLoggedIn={isLoggedIn} />
{button}
</div>
);
}
}

function UserGreeting(props) {
return <h1>Welcome back!</h1>;
}

function GuestGreeting(props) {
return <h1>Please sign up.</h1>;
}

function Greeting(props) {
const isLoggedIn = props.isLoggedIn;
if (isLoggedIn) {
return <UserGreeting />;
}
return <GuestGreeting />;
}

function LoginButton(props) {
return (
<button onClick={props.onClick}>
Login
</button>
);
}

function LogoutButton(props) {
return (
<button onClick={props.onClick}>
Logout
</button>
);
}

ReactDOM.render(
<LoginControl />,
document.getElementById('root')
);
</script>
</body>
</html>

9.键(Keys)

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>Hello World</title>
<script src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>
</head>
<body>
<div id="root"></div>
<script type="text/babel">
function Blog(props) {
const sidebar = (
<ul>
{props.posts.map((post) =>
<li key={post.id}>
{post.title}
</li>
)}
</ul>
);
const content = props.posts.map((post) =>
<div key={post.id}>
<h3>{post.title}</h3>
<p>{post.content}</p>
</div>
);
return (
<div>
{sidebar}
<hr />
{content}
</div>
);
}

const posts = [
{id: 1, title: 'name', content: 'xutongbao'},
{id: 2, title: '姓名', content: '徐同保'}
];
ReactDOM.render(
<Blog posts={posts} />,
document.getElementById('root')
);
</script>
</body>
</html>

10.表单(受控元素)

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>Hello World</title>
<script src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>
</head>
<body>
<div id="root"></div>
<script type="text/babel">
class NameForm extends React.Component {
constructor(props) {
super(props);
this.state = {value: ''};

this.handleChange = this.handleChange.bind(this);
this.handleSubmit = this.handleSubmit.bind(this);
}

handleChange(event) {
this.setState({value: event.target.value});
}

handleSubmit(event) {
alert('A name was submitted: ' + this.state.value);
event.preventDefault();
}

render() {
return (
<form onSubmit={this.handleSubmit}>
<label>
Name:
<input type="text" value={this.state.value} onChange={this.handleChange} />
</label>
<input type="submit" value="Submit" />
</form>
);
}
}

ReactDOM.render(
<NameForm />,
document.getElementById('root')
);
</script>
</body>
</html>

11.表单(文件上传)

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>Hello World</title>
<script src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>
</head>
<body>
<div id="root"></div>
<script type="text/babel">
class FileInput extends React.Component {
constructor(props) {
super(props);
this.handleSubmit = this.handleSubmit.bind(
this
);
}
handleSubmit(event) {
event.preventDefault();
alert(
`Selected file - ${
this.fileInput.files[0].name
}`
);
}

render() {
return (
<form
onSubmit={this.handleSubmit}>
<label>
Upload file:
<input
type="file"
ref={input => {
this.fileInput = input;
}}
/>
</label>
<br />
<button type="submit">
Submit
</button>
</form>
);
}
}

ReactDOM.render(
<FileInput />,
document.getElementById('root')
);
</script>
</body>
</html>

12.状态提升(将公用的值以及修改该值的方法都放在父组件里)

在一个 React 应用中,对于任何可变的数据都应该循序“单一数据源”原则。通常情况下,state 首先被添加到需要它进行渲染的组件。然后,如果其它的组件也需要它,你可以提升状态到它们最近的祖先组件。你应该依赖 从上到下的数据流向 ,而不是试图在不同的组件中同步状态。

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>Hello World</title>
<script src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>
</head>
<body>
<div id="root"></div>
<script type="text/babel">
const scaleNames = {
c: 'Celsius',
f: 'Fahrenheit'
};

function toCelsius(fahrenheit) {
return (fahrenheit - 32) * 5 / 9;
}

function toFahrenheit(celsius) {
return (celsius * 9 / 5) + 32;
}

function tryConvert(temperature, convert) {
const input = parseFloat(temperature);
if (Number.isNaN(input)) {
return '';
}
const output = convert(input);
const rounded = Math.round(output * 1000) / 1000;
return rounded.toString();
}

function BoilingVerdict(props) {
if (props.celsius >= 100) {
return <p>The water would boil.</p>;
}
return <p>The water would not boil.</p>;
}

class TemperatureInput extends React.Component {
constructor(props) {
super(props);
this.handleChange = this.handleChange.bind(this);
}

handleChange(e) {
this.props.onTemperatureChange(e.target.value);
}

render() {
const temperature = this.props.temperature;
const scale = this.props.scale;
return (
<fieldset>
<legend>Enter temperature in {scaleNames[scale]}:</legend>
<input value={temperature}
onChange={this.handleChange} />
</fieldset>
);
}
}

class Calculator extends React.Component {
constructor(props) {
super(props);
this.handleCelsiusChange = this.handleCelsiusChange.bind(this);
this.handleFahrenheitChange = this.handleFahrenheitChange.bind(this);
this.state = {temperature: '', scale: 'c'};
}

handleCelsiusChange(temperature) {
this.setState({scale: 'c', temperature});
}

handleFahrenheitChange(temperature) {
this.setState({scale: 'f', temperature});
}

render() {
const scale = this.state.scale;
const temperature = this.state.temperature;
const celsius = scale === 'f' ? tryConvert(temperature, toCelsius) : temperature;
const fahrenheit = scale === 'c' ? tryConvert(temperature, toFahrenheit) : temperature;

return (
<div>
<TemperatureInput
scale="c"
temperature={celsius}
onTemperatureChange={this.handleCelsiusChange} />
<TemperatureInput
scale="f"
temperature={fahrenheit}
onTemperatureChange={this.handleFahrenheitChange} />
<BoilingVerdict
celsius={parseFloat(celsius)} />
</div>
);
}
}

ReactDOM.render(
<Calculator />,
document.getElementById('root')
);

</script>
</body>
</html>

13.组合(children)

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>Hello World</title>
<script src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>
<style type="text/css">
.FancyBorder {
padding: 10px 10px;
border: 10px solid;
}

.FancyBorder-blue {
border-color: blue;
}

.Dialog-title {
margin: 0;
font-family: sans-serif;
}

.Dialog-message {
font-size: larger;
}
</style>
</head>
<body>
<div id="root"></div>
<script type="text/babel">
function FancyBorder(props) {
return (
<div className={'FancyBorder FancyBorder-' + props.color}>
{props.children}
</div>
);
}

function WelcomeDialog() {
return (
<FancyBorder color="blue">
<h1 className="Dialog-title">
Welcome
</h1>
<p className="Dialog-message">
Thank you for visiting our spacecraft!
</p>
</FancyBorder>
);
}

ReactDOM.render(
<WelcomeDialog />,
document.getElementById('root')
);
</script>
</body>
</html>

14.组合(多个占位符)

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>Hello World</title>
<script src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
<script src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>
<style type="text/css">
html, body, #root {
width: 100%;
height: 100%;
}

.SplitPane {
width: 100%;
height: 100%;
}

.SplitPane-left {
float: left;
width: 30%;
height: 100%;
}

.SplitPane-right {
float: left;
width: 70%;
height: 100%;
}

.Contacts {
width: 100%;
height: 100%;
background: lightblue;
}

.Chat {
width: 100%;
height: 100%;
background: pink;
}

</style>
</head>
<body>
<div id="root"></div>
<script type="text/babel">
function Contacts() {
return <div className="Contacts" />;
}

function Chat() {
return <div className="Chat" />;
}

function SplitPane(props) {
return (
<div className="SplitPane">
<div className="SplitPane-left">
{props.left}
</div>
<div className="SplitPane-right">
{props.right}
</div>
</div>
);
}

function App() {
return (
<SplitPane
left={
<Contacts />
}
right={
<Chat />
} />
);
}

ReactDOM.render(
<App />,
document.getElementById('root')
);

</script>
</body>
</html>

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


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