React is one of the most popular libraries in modern web development, helping to efficiently build user interfaces (UI). In this tutorial, we will explore how to set up and develop a React project using Visual Studio Code (VS Code).

1. Introduction to Visual Studio Code

VS Code is a source code editor developed by Microsoft, supporting various programming languages. It is lightweight yet provides powerful features, making it popular among developers. The main features of VS Code include:

• Scalability and Customization
• Integrated Terminal
• Version Control (Git) Integration
• Debugging Support
• Variety of Themes and Icon Packages

2. Setting Up the Environment

2.1 Installing VS Code

First, you need to install VS Code. Visit here to download and install the version suitable for your operating system. The installation process is straightforward and consists of simple click steps.

2.2 Installing Node.js and npm

To use React, you need Node.js and npm (Node Package Manager). Node.js is a JavaScript runtime environment, while npm is a tool for managing JavaScript packages. Download and install the installer from the link below:

• Node.js Download

Once the installation is complete, you can check if the installation was successful by entering the following commands in the terminal:

node -v

npm -v

2.3 Creating a React Project with Create React App

After installing VS Code, Node.js, and npm, you can create a new React application. By using Create React App, it sets up a basic React project with all configurations automatically done. Run the following command to create the project:

npx create-react-app my-app

Here, my-app is the name of the project you are creating. You can change it to whatever name you prefer. Once the command is complete, navigate to that directory:

cd my-app

3. Opening the Project in VS Code

After launching VS Code, select File > Open Folder from the top menu and choose the created my-app folder. You can now check the project structure.

4. Understanding the Project Structure

The basic project structure generated using Create React App is as follows:

• node_modules/: Contains all the packages used in the project.
• public/: Contains static files and the HTML template.
• src/: Contains the application’s code, primarily JavaScript and CSS files.
• package.json: Contains information about the project and manages dependencies and scripts.
• README.md: A documentation file about the project.

5. Setting Up the Development Environment

5.1 Code Formatting and Linting

To maintain a consistent code style and improve code quality, we set up ESLint and Prettier. Install both packages with the following command in the terminal:

npm install eslint prettier eslint-config-prettier eslint-plugin-prettier --save-dev

Then, create .eslintrc.js and .prettierrc files in the root directory of the project to add configurations. The content of the .eslintrc.js file is as follows:

module.exports = {
    env: {
        browser: true,
        es2021: true,
    },
    extends: [
        'eslint:recommended',
        'plugin:react/recommended',
        'prettier',
    ],
    parserOptions: {
        ecmaFeatures: {
            jsx: true,
        },
        ecmaVersion: 12,
        sourceType: 'module',
    },
    plugins: [
        'react',
        'prettier',
    ],
    rules: {
        'prettier/prettier': 'error',
    },
};

You can add the following settings in the .prettierrc file:

{
    "semi": true,
    "singleQuote": true
}

5.2 Installing VS Code Extensions

VS Code extensions are convenient development tools; we will install several useful extensions for React development. Recommended extensions include:

• ESLint
• Prettier – Code formatter
• Simple React Snippet
• Reactjs code snippets

Extensions can be installed by clicking the Extensions icon in the left sidebar and entering the names in the search bar.

6. Basic Concepts of React

To understand React, you need to know a few foundational concepts:

• Component: The fundamental building block of a React application. Components are defined as JavaScript functions and facilitate code reuse.
• JSX: Stands for JavaScript XML, it uses a syntax similar to HTML to represent the UI.
• State: Represents the data state of a component, causing re-rendering when data changes.
• Props: Data passed from parent components to child components.

7. Creating a React Component

Now let’s create a React component. Create a file named MyComponent.js in the src/ folder and enter the following code:

import React from 'react';

const MyComponent = () => {
    return (
        

            
Hello, React!
            
This is my first React component.
        
    );
};

export default MyComponent;

Now, let’s use this component in the src/App.js file. Update the code as follows:

import React from 'react';
import MyComponent from './MyComponent';

function App() {
    return (
        

            
        
    );
}

export default App;

8. Setting Up React Routing

To implement navigation between pages in a React application, we use the react-router-dom library. Install this package with the following command:

npm install react-router-dom

Now, you can set up routing. Modify the src/App.js file as follows:

import React from 'react';
import { BrowserRouter as Router, Route, Switch } from 'react-router-dom';
import MyComponent from './MyComponent';

function App() {
    return (
        
            
                
                
            
        
    );
}

export default App;

In the code above, AboutComponent is a newly added component. You can create new components in the same way for routing.

9. Communicating with APIs

To communicate with external APIs in a React application, you can use libraries like axios. Install axios with the following command:

npm install axios

Here’s a simple example of fetching data using axios. Modify src/MyComponent.js as follows:

import React, { useState, useEffect } from 'react';
import axios from 'axios';

const MyComponent = () => {
    const [data, setData] = useState([]);

    useEffect(() => {
        const fetchData = async () => {
            const result = await axios('https://api.example.com/data');
            setData(result.data);
        };

        fetchData();
    }, []);

    return (
        

            
Data Fetching Example
            

                {data.map(item => (
                    
{item.title}
                ))}
            
        
    );
};

export default MyComponent;

10. Building and Deploying the Application

Once development is complete, you need to build the application to prepare for deployment. You can perform the build with the following command:

npm run build

Executing the above command will create a build/ folder with optimized static files in it. You can upload these files to your chosen hosting service for deployment.

11. Conclusion

In this tutorial, we learned how to develop a web application using Visual Studio Code and React. You can build dynamic user interfaces using React and create an efficient development environment with the various features of VS Code. I hope you will continue to learn more in-depth React and frontend development techniques!

React is a UI library based on components, widely used for building user interfaces. In particular, asynchronous processing plays a crucial role in modern web applications and is essential for efficiently handling interactions with APIs and data loading.

1. Understanding Asynchronous Processing

Asynchronous processing is a programming paradigm that allows other tasks to be performed while code is executing. This is primarily necessary in the following situations:

• When you want to perform other tasks while waiting for an HTTP request to send and receive a response
• When reading or writing files may take time
• When setting a timer that takes a certain amount of time

1.1 Synchronous vs Asynchronous

Synchronous processing is a method where tasks are executed sequentially. That is, the next task does not begin until the current task is complete. In contrast, asynchronous processing allows starting a task and performing other tasks simultaneously without waiting for the result of that task.

1.2 The Necessity of Asynchronous Processing

Asynchronous processing is necessary in web applications to optimize user experience. For example, when a user clicks a button to load data, requesting the data asynchronously can keep the UI from freezing and provide quick feedback to the user.

2. Handling Asynchronous Processing in React

There are several ways to implement asynchronous processing in React, typically through Promise, async/await, and state management tools in React.

2.1 Using Promises

Promises are objects that represent the success or failure of an asynchronous operation. Here’s how to handle asynchronous operations using a Promise:

const fetchData = () => {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            const data = "Data loading complete!";
            resolve(data);
        }, 2000);
    });
};

fetchData().then(response => {
    console.log(response);
}).catch(error => {
    console.log(error);
});

2.2 Using async/await

The async/await syntax makes it easier to use Promises. When using this syntax, asynchronous code appears to execute as if it were synchronous:

const fetchData = async () => {
    try {
        const response = await new Promise((resolve, reject) => {
            setTimeout(() => {
                resolve("Data loading complete!");
            }, 2000);
        });
        console.log(response);
    } catch (error) {
        console.log(error);
    }
};

fetchData();

2.3 Asynchronous Communication with APIs in React

Asynchronous communication with APIs in React is primarily achieved through the useEffect hook. The useEffect hook is used to trigger side effects when a component renders:

import React, { useEffect, useState } from 'react';

const DataFetchingComponent = () => {
    const [data, setData] = useState(null);
    const [loading, setLoading] = useState(true);

    useEffect(() => {
        const fetchData = async () => {
            try {
                const response = await fetch('https://api.example.com/data');
                const result = await response.json();
                setData(result);
            } catch (error) {
                console.error('Error fetching data:', error);
            } finally {
                setLoading(false);
            }
        };
        fetchData();
    }, []);

    if (loading) {
        return 
Loading...
;
    }

    return (
        

            
Data:
            
{JSON.stringify(data, null, 2)}

    );

};
export default DataFetchingComponent;


2.4 State Management Tools and Asynchronous Processing
State management tools for React (e.g., Redux, MobX) also support asynchronous processing. Redux allows handling asynchronous actions through Redux Thunk or Redux Saga.
3. Error Handling and Loading State Management
When performing asynchronous operations, managing error handling and loading states is very important. You can improve UX by showing a loading spinner or displaying error messages. Below is a simple example of error handling and loading state management:

const DataFetchingComponent = () => {
    const [data, setData] = useState(null);
    const [error, setError] = useState(null);
    const [loading, setLoading] = useState(true);

    useEffect(() => {
        const fetchData = async () => {
            try {
                const response = await fetch('https://api.example.com/data');
                if (!response.ok) {
                    throw new Error('Network response was not ok');
                }
                const result = await response.json();
                setData(result);
            } catch (error) {
                setError(error.message);
            } finally {
                setLoading(false);
            }
        };
        fetchData();
    }, []);

    if (loading) return 
Loading...
;
    if (error) return 
Error occurred: {error}
;

    return 
{JSON.stringify(data)}
;
};

4. Conclusion
Asynchronous processing in React primarily plays a vital role in managing interactions with APIs and loading data. By using Promises, async/await, and various state management tools, asynchronous tasks can be handled efficiently. By understanding and implementing proper asynchronous processing methods, a better user experience can be provided.
5. Additional Resources

React Official Documentation: AJAX Requests
Redux Official Documentation
MDN Web Docs: Asynchronous Functions

	

React is a component-based front-end library that provides a means to build efficient and enjoyable user interfaces. However, while writing components in React, you may often encounter the problem of unnecessary function recreations. This can lead to performance degradation, and therefore, measures are needed to enhance the efficiency of React applications.

1. Reasons for Function Recreation

In React, JSX is executed every time a component is rendered. In this process, functions are also re-executed, generating new function instances. This can occur in the following situations:

• Regular functions defined within the component
• Event handlers
• Functions included in the dependency array of the effect hook (useEffect)

If these functions are newly created on every render, it may lead to performance issues, especially in applications where performance is critical.

2. Methods to Prevent Unnecessary Function Recreation

2.1. Using the useCallback Hook

The useCallback hook allows you to recreate a function only when specific dependencies change. This helps prevent unnecessary renders. Let’s take a look at the following example:

import React, { useState, useCallback } from 'react';

    function Counter() {
        const [count, setCount] = useState(0);

        const increment = useCallback(() => {
            setCount(c => c + 1);
        }, []);

        return (
            

                
Count: {count}
                Increment
            
        );
    }

In the example above, the increment function is memoized using useCallback, preventing unnecessary function recreation during the re-rendering of the Counter component.

2.2. Using the useMemo Hook

The useMemo hook allows you to memoize computed values, optimizing performance. You can improve performance by memoizing functions that perform complex calculations.

import React, { useState, useMemo } from 'react';

    function FactorialCalculator() {
        const [number, setNumber] = useState(1);

        const factorial = useMemo(() => {
            const calculateFactorial = (n) => {
                return n <= 0 ? 1 : n * calculateFactorial(n - 1);
            };
            return calculateFactorial(number);
        }, [number]);

        return (
            

                 setNumber(e.target.value)} />
                
Factorial: {factorial}
            
        );
    }

In the example above, the factorial calculation is executed only when the number state changes, preventing unnecessary recreation of the internal function.

2.3. Avoid Using Bind Method in Class Components

In class components, it is advisable to perform binding in the constructor using this.methodName = this.methodName.bind(this); or to define methods using arrow functions to avoid recreation of methods.

class MyComponent extends React.Component {
        constructor(props) {
            super(props);
            this.handleClick = this.handleClick.bind(this); // Binding in the constructor
        }

        handleClick() {
            console.log('Clicked!');
        }

        render() {
            return Click me;
        }
    }

3. Performance Testing and Optimization Verification

After applying methods for performance optimization, it is recommended to use profiling tools to check for changes in performance. You can measure rendering performance using the profiling feature provided by React’s React DevTools. This allows you to verify if unnecessary renders are occurring and consider additional optimizations if needed.

4. Conclusion

Preventing unnecessary function recreation in React applications is a very important task for performance improvement. By properly utilizing the useCallback and useMemo hooks, unnecessary renders can be avoided, and the binding methods in class components should also be considered. Remember that performance optimization is a repetitive process, and consistently monitoring and improving application performance is essential.

5. References

• React Docs: useCallback
• React Docs: useMemo
• React Docs: Class and Function Components

1. Introduction

React is a very powerful and flexible library for building user interfaces. However, performance issues can arise due to the way various components are rendered. In particular, unnecessary component re-rendering can degrade the performance of the application. In this course, we will explore various techniques to prevent unnecessary component re-rendering in React.

2. Understanding Re-rendering

In React, when the state or props change, the corresponding component is re-rendered. Although this basic operation is normal, excessive re-rendering can lead to performance issues. Therefore, it is essential to manage re-rendering effectively.

2.1. When Re-rendering Occurs

The main cases where re-rendering occurs in React are as follows:

• When the component’s state changes
• When the component’s props change
• When the parent component re-renders, the child components also re-render

2.2. The Cost of Excessive Re-rendering

Unnecessary re-rendering can lead to the following problems:

• Performance degradation: Frequent rendering can slow down the application’s response time.
• Increased memory usage: Unnecessary memory usage can increase due to re-rendering.
• Decreased user experience: A slower application negatively impacts user experience.

3. Preventing Unnecessary Re-rendering

3.1. Using React.memo

React provides a higher-order component called React.memo to prevent component re-rendering. When using React.memo, the component will not re-render if the same props are passed.

import React, { memo } from 'react';

const MyComponent = memo(({ title }) => {
  return <h1>{title}</h1>;
});

3.2. useMemo and useCallback

Using useMemo and useCallback, which are React hooks, can optimize re-rendering. They return memoized values and memoized functions, respectively, preventing unnecessary rendering.

import React, { useMemo, useCallback } from 'react';

const MyComponent = ({ items }) => {
  const total = useMemo(() => calculateTotal(items), [items]);
  const handleClick = useCallback(() => {
    console.log('Clicked!');
  }, []);

  return (
    <div>
      <h1>Total: {total}</h1>
      <button onClick={handleClick}>Click me</button>
    </div>
  );
};

3.3. PureComponent and shouldComponentUpdate

In class components, you can inherit from PureComponent to prevent unnecessary re-rendering. PureComponent compares the shallow changes of props and state by default and prevents re-rendering if there are no changes.

import React, { PureComponent } from 'react';

class MyComponent extends PureComponent {
  render() {
    return <h1>{this.props.title}</h1>;
  }
}

3.4. Optimizing State Management

Using state management libraries (e.g., Redux, MobX) to manage global state can reduce unnecessary re-rendering. By appropriately separating the state, only specific components can be re-rendered.

4. Example of Re-rendering Optimization

Below is an example that demonstrates re-rendering optimization.

import React, { useState, memo } from 'react';

const Item = memo(({ item }) => {
  console.log('Item rendered');
  return <div>{item.name}</div>;
});

const ItemList = ({ items }) => {
  return items.map(item => <Item key={item.id} item={item} />);
};

const MyComponent = () => {
  const [items, setItems] = useState([{ id: 1, name: 'Item 1' }, { id: 2, name: 'Item 2' }]);
  const [counter, setCounter] = useState(0);

  return (
    <div>
      <h1>Counter: {counter}</h1>
      <button onClick={() => setCounter(counter + 1)}>Increment Counter</button>
      <ItemList items={items} />
    </div>
  );
};

5. Conclusion

To optimize performance in React applications, it is essential to prevent unnecessary component re-rendering. By utilizing various techniques such as React.memo, useMemo, useCallback, and PureComponent, you can create a more performant application. Apply optimizations to your React projects to provide a better user experience!

React is one of the most widely used JavaScript libraries for building modern web applications. To use React effectively, it is essential to understand the basic concepts of JavaScript, especially variables and constants. This article will deeply explore how to use variables and constants in React.

1. What is a variable?

A variable is a space to store data, which has the characteristic of being able to change its value as needed. In JavaScript, variables can be declared using three keywords: var, let, and const.

1.1 var keyword

var is the oldest method of declaring variables and has function scope. This means that a variable declared with var is only valid within the function. It can be accessed globally at any time.

var x = 10;
if (true) {
    var x = 20; // Redefining x within the same scope
}
console.log(x); // Output: 20

1.2 let keyword

let has block scope, allowing variables to be declared that are only valid within a block. This allows for finer control over the variable’s scope.

let y = 10;
if (true) {
    let y = 20; // Redefining within a different block scope
}
console.log(y); // Output: 10

1.3 const keyword

const is used to declare constants, and the value cannot be changed after declaration. Similarly, const also has block scope.

const z = 30;
if (true) {
    const z = 40; // Redefining within a different block scope
}
console.log(z); // Output: 30

2. Using variables in React

In React, variables and constants are used to compose the UI. They are mainly used to store the state of a component or to pass data via props.

2.1 Component State

The state of a React component is declared using the useState hook. This state can change when the component is rendered.

import React, { useState } from 'react';

const Counter = () => {
    const [count, setCount] = useState(0); // Declare the count variable

    return (
        

            
Current Count: {count}
             setCount(count + 1)}>Increase
        
    );
}

2.2 Passing Data through Props

Props are used to pass data between components. Props are component properties, and can be used like variables.

const Greeting = ({ name }) => {
    return 
Hello, {name}!
;
}

const App = () => {
    return ;
}

3. How to use constants

Constants represent unchanging values, helping to improve code readability and reduce bugs. In React, constants are mostly defined for styles or configuration values.

const API_URL = "https://api.example.com/data";

const fetchData = async () => {
    const response = await fetch(API_URL);
    const data = await response.json();
    console.log(data);
}

4. Example using variables and constants

Let’s discuss how to utilize variables and constants according to the life cycle. Below is a simple example of sending an API request and displaying data in React.

import React, { useState, useEffect } from 'react';

const DataFetcher = () => {
    const [data, setData] = useState([]);
    const API_URL = "https://api.example.com/data";

    useEffect(() => {
        const fetchData = async () => {
            const response = await fetch(API_URL);
            const result = await response.json();
            setData(result);
        };

        fetchData();
    }, []);

    return (
        

            {data.map(item => (
                
{item.name}
            ))}
        
    );
}

5. Best Practices for Variables and Constants

• Name variables meaningfully: Variable names should clearly indicate their purpose.
• Use uppercase for constants: Constants should be defined using uppercase letters and underscores (_).
• Be aware of scope: Clearly understand and write the scope of variables and constants.

Conclusion

Correctly using variables and constants in React is crucial for writing stable and maintainable code. Based on the above content, try to effectively utilize variables and constants.

If you found this tutorial helpful, please leave a comment!