자바개발자 리엑트 배우기 - Component

Absolutely, let's start from the basics:

A Component in React is a self-contained piece of code that ideally does one thing and does it well. A component could be as small as a button or as large as an entire page. A React application is typically made up of multiple components that are nested and work together to form the complete application.

There are two types of components in React:

1. Functional Components: These are simple JavaScript functions that return a piece of the UI, usually written in JSX. Here is an example:

   function Welcome(props) {
     return <h1>Hello, {props.name}</h1>;
   }

2. Class Components: These are more complex and are written as ES6 classes. They have additional features such as lifecycle methods and state. Here is an example:

   class Welcome extends React.Component {
     render() {
       return <h1>Hello, {this.props.name}</h1>;
     }
   }

The import keyword is part of ES6 modules system, which allows you to break your JavaScript code into separate files (modules) that can depend on each other. This makes code more organized and easier to maintain.

Here's a basic example:

// math.js
export function add(x, y) {
  return x + y;
}

// app.js
import { add } from './math.js';

console.log(add(2, 3));  // 5

In this example, the add function is exported from the math.js module and then imported into the app.js module, where it's used.

When you're using React, you'll often see imports like these:

import React, { useState } from 'react';

This is importing the React object and the useState function from the 'react' module. useState is a function that allows you to add state to a functional component.

In the context of React:

• import React from 'react'; is used to access the React library in your file. You need it whenever you are using JSX in your file.

• import { useState } from 'react'; is used to import the useState Hook from React. This allows your functional component to maintain its own state.

I hope this helps! Let me know if you have more questions.