A Quick Intro to React.js
React empowers the creation of dynamic websites rendered entirely within the browser. Its core element is JSX, a syntax resembling HTML and XML.
Language | Full Form | Use | Tags |
---|---|---|---|
HTML | Hyper Text Markup Language | Website Development | Predefined tags (e.g., H1, H2, P) |
XML | Extensible Markup Language | Data Structuring | Customizable Tags |
JSX | JavaScript XML | Combines HTML and JavaScript | HTML & Custom Tags |
Illustrative Examples
HTML
<div> <h1>This is heading 1</h1> <p>This is an example paragraph in HTML</p> </div>
XML
<example><title>XML Example <note>This is a note</note><data1>Example Data</data1><data2>Example Data</data2></title></example>
JSX
function ExampleReactComponent() { return ( <div> <h1>This is heading 1</h1> <p>This is an example paragraph in JSX</p> </div> ); }
The similarity between HTML, XML, and JSX is evident. JSX uniquely integrates HTML within JavaScript, hence its name: JavaScript XML.
This fusion of HTML and JavaScript enables dynamic HTML manipulation. For instance, a button click could toggle a class name.
React Components
React facilitates the definition of custom components that return JSX. Essentially, a React component is a JavaScript function generating JSX.
Upon rendering a root React component, JSX is automatically converted into HTML and integrated into the webpage. React allows creating custom components (akin to custom tags) for inclusion within other components.
Here's a component utilizing the ExampleReactComponent
:
function RootReactComponent() { return ( <div> <h1>This is the main Component</h1> <ExampleReactComponent /> </div> ); }
Props
Similar to HTML attributes, React components employ props.
function PropsExample(props) { console.log(props); // Prints { exampleValue: "example-value" } return ( <div> <h1>Props Example</h1> {props.exampleValue} </div> ); } function MainComponent() { return ( <div> <h1>This is the Main Component</h1> <PropsExample exampleValue={"example-value"} /> </div> ); }
Rendering MainComponent
invokes PropsExample
with { exampleValue: "example-value" }
as the props
argument. Note that JavaScript variables are embedded within JSX using {}
.
State
Data is typically stored in variables for display. React utilizes "state" for data management, acting as a getter/setter mechanism. When state is modified, React automatically updates the component's HTML.
This example demonstrates automatic HTML updates upon state changes:
import { useState } from 'react'; function IncrementDecrement() { const [value, setValue] = useState(0); // Initial value: 0 function increment(e) { setValue(value + 1); } function decrement(e) { setValue(value - 1); } return ( <div> <button onClick={increment}>Increment</button> <button onClick={decrement}>Decrement</button> {value} </div> ); }
Building React Apps with Vite
Tools like Vite streamline the bundling of React components and JSX into browser-executable JavaScript.
To initiate a React project:
npm create vite@latest my-react-app -- --template react cd my-react-app npm install npm run dev
Conclusion
This introduction to React.js provides a foundational understanding. After setting up a Vite project, experiment with creating React components to deepen your comprehension. Further learning resources are available at https://www.php.cn/link/27a5eaafdb88c45dd61732d6a6493421.
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