Custom Hooks in React

This guide provides a comprehensive introduction to custom hooks in React, including how to create, use, and optimize them. Learn best practices, advanced topics, and real-world applications.

Introduction to Custom Hooks

What is a Custom Hook?

In the world of React, custom hooks are a powerful feature that allows you to extract and share logic between components. Imagine you have a snippet of code that fetches data from an API and updates the state whenever the data changes. Instead of duplicating this code across multiple components, you can encapsulate it in a custom hook. This not only makes your code cleaner but also ensures that the shared logic is easy to maintain and test.

Think of custom hooks as a way to package up, share, and reuse React components' logic. Just like how you can reuse a function in JavaScript to avoid repetition, you can do the same with the logic in your React components using custom hooks.

Why Use Custom Hooks?

Custom hooks are beneficial for several reasons:

Code Reusability: DRY (Don't Repeat Yourself) is a principle in software development. Custom hooks allow you to reuse code across different components, reducing duplication and improving maintainability.
Simplifying Components: By moving complex logic into custom hooks, you can simplify your components and make them easier to read and understand.
Encapsulation: Custom hooks help encapsulate state and logic, making it easier to understand the purpose of a piece of code without having to sift through the entire component.
Testing: Hooks can be easier to test compared to components because they are pure JavaScript functions. By extracting logic into custom hooks, you make it easier to write unit tests.
Community and Ecosystem: Custom hooks are a part of the React ecosystem, and there are many community-maintained hooks available that can help you speed up development and build complex features with less code.

Getting Started with Custom Hooks

Setting Up Your Development Environment

Before diving into custom hooks, ensure you have a React environment set up. You can use tools like Create React App to quickly set up a new project. Here’s how you can do it:

Install Node.js and npm: Custom hooks, like all modern JavaScript features, rely on Node.js and npm (Node Package Manager). Download and install them from nodejs.org.
Create a New React App: Use Create React App to set up a new project. Open your terminal, navigate to the directory where you want your project to be, and run the following commands:
```
npx create-react-app my-app
cd my-app
```
Start the Development Server: Once your project is set up, start the development server to see your React app in action.
```
npm start
```
This command will open your React app in the browser, typically at http://localhost:3000.

Basic Structure of a Custom Hook

A custom hook is simply a JavaScript function whose name starts with use. This naming convention is important because it allows React to automatically detect when a hook is being used and check for violations of the Rules of Hooks.

Here’s a simple structure for a custom hook:

function useMyCustomHook(initialValue) {
  // Hook logic goes here
  // For example, using useState or useEffect

  return {
    // Values or functions to be returned
  };
}

Writing Your First Custom Hook

Creating a Basic Custom Hook

Let’s write a simple custom hook that logs a message to the console whenever a component mounts or updates. This is a great way to get a feel for how custom hooks work.

Step-by-Step Guide

Create a New File for Your Hook: In your React project, create a new folder called hooks inside the src directory. Inside the hooks folder, create a file named useLogging.js.

Write the Hook Code: Open useLogging.js and write the following code:

import { useEffect } from 'react';

function useLogging(componentName) {
  useEffect(() => {
    console.log(`${componentName} mounted`);

    return () => {
      console.log(`${componentName} unmounted`);
    };
  }, [componentName]);

  console.log(`${componentName} updated`);
}

export default useLogging;

In this example, useLogging takes a componentName as an argument. It logs a message to the console when the component mounts, updates, and unmounts.

Use the Hook in a Component: Open the src/App.js file and modify it to use the useLogging hook:

import React, { useState } from 'react';
import useLogging from './hooks/useLogging';

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

  useLogging('App');

  return (
    <div className="App">
      <header className="App-header">
        <h1>Click the button to increment the count: {count}</h1>
        <button onClick={() => setCount(count + 1)}>Increment</button>
      </header>
    </div>
  );
}

export default App;

Here, the useLogging hook is used in the App component. Every time the component updates, a message is logged to the console.

Run Your App: Save your changes and visit http://localhost:3000. Open the browser’s console to see the logs.

Example: Creating a Counter Hook

Let’s create a more practical custom hook, one that manages a counter state. This hook will increment, decrement, and reset the counter, making it easy to reuse in different components.

Step-by-Step Guide

Create a New File for the Counter Hook: Inside the hooks folder, create a new file named useCounter.js.

Write the Hook Code: Open useCounter.js and write the following code:

import { useState } from 'react';

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

  const increment = () => setCount(prevCount => prevCount + 1);
  const decrement = () => setCount(prevCount => prevCount - 1);
  const reset = () => setCount(initialValue);

  return {
    count,
    increment,
    decrement,
    reset,
  };
}

export default useCounter;

This hook uses the useState hook to manage the counter state and provides increment, decrement, and reset functions to manipulate the state.

Use the Counter Hook in a Component: Open src/App.js and modify it to use the useCounter hook:

import React from 'react';
import useCounter from './hooks/useCounter';

function App() {
  const counter = useCounter(0);

  return (
    <div className="App">
      <header className="App-header">
        <h1>Counter: {counter.count}</h1>
        <button onClick={counter.increment}>Increment</button>
        <button onClick={counter.decrement}>Decrement</button>
        <button onClick={counter.reset}>Reset</button>
      </header>
    </div>
  );
}

export default App;

Here, the useCounter hook is used in the App component, managing the counter state and providing functions to control it.

Run Your App: Save your changes and visit http://localhost:3000. You should see a counter that you can increment, decrement, and reset.

Best Practices for Custom Hooks

Reusing Logic with Hooks

One of the primary goals of custom hooks is to reuse logic between components. Instead of creating a high-order component (HOC) or a render prop, which can add unnecessary complexity, you can use a custom hook.

Let’s modify our useCounter hook to allow custom step sizes for incrementing and decrementing the counter.

Step-by-Step Guide

Modify the Counter Hook: Open useCounter.js and modify it to accept a step parameter:

import { useState } from 'react';

function useCounter(initialValue = 0, step = 1) {
  const [count, setCount] = useState(initialValue);

  const increment = () => setCount(prevCount => prevCount + step);
  const decrement = () => setCount(prevCount => prevCount - step);
  const reset = () => setCount(initialValue);

  return {
    count,
    increment,
    decrement,
    reset,
  };
}

export default useCounter;

Use the Modified Hook in a Component: Open src/App.js and modify it to pass a step value:

import React from 'react';
import useCounter from './hooks/useCounter';

function App() {
  const counter = useCounter(0, 5);

  return (
    <div className="App">
      <header className="App-header">
        <h1>Counter: {counter.count}</h1>
        <button onClick={counter.increment}>Increment by 5</button>
        <button onClick={counter.decrement}>Decrement by 5</button>
        <button onClick={counter.reset}>Reset</button>
      </header>
    </div>
  );
}

export default App;

Here, the useCounter hook is now more flexible, allowing you to specify the step size when using it.

Naming Custom Hooks

Custom hooks must have a name that starts with use. This is not just a convention; it’s enforced by React. React uses this naming convention to identify custom hooks and ensure that they are used correctly.

For example, if you want to create a hook for fetching data, name it useFetch instead of fetchData.

Guidelines for Custom Hooks

Use use Prefix: Always start a custom hook name with use to signal that it’s a hook to both React and other developers.
Call Hooks at the Top Level: Never call hooks inside loops, conditions, or nested functions. Always use hooks at the top level of your React function.
Only Call Hooks from React Functions: Call custom hooks from React function components or from custom hooks. Do not call them from regular JavaScript functions.

Advanced Topics

Encapsulating State Logic

Custom hooks are excellent for encapsulating state logic, making it reusable and easier to manage. They can take parameters and return values, allowing you to control the behavior of the hook.

Example: Encapsulating Form State Logic

Let’s create a custom hook that manages form state. This hook will return the current form values and functions to update them.

Step-by-Step Guide

Create a New File for the Form Hook: Inside the hooks folder, create a new file named useForm.js.

Write the Hook Code: Open useForm.js and write the following code:

import { useState } from 'react';

function useForm(initialValues) {
  const [values, setValues] = useState(initialValues);

  const handleChange = (e) => {
    const { name, value } = e.target;
    setValues(prevValues => ({
      ...prevValues,
      [name]: value,
    }));
  };

  const resetForm = () => {
    setValues(initialValues);
  };

  return {
    values,
    handleChange,
    resetForm,
  };
}

export default useForm;

This hook manages a form’s state based on the initial values provided. It includes a handleChange function to update the state whenever a form input changes and a resetForm function to reset the form to its initial values.

Use the Form Hook in a Component: Open src/App.js and modify it to use the useForm hook:

import React from 'react';
import useForm from './hooks/useForm';

function App() {
  const form = useForm({ name: '', email: '' });

  const handleSubmit = (e) => {
    e.preventDefault();
    console.log('Form submitted:', form.values);
    form.resetForm();
  };

  return (
    <div className="App">
      <header className="App-header">
        <form onSubmit={handleSubmit}>
          <div>
            <label>
              Name:
              <input type="text" name="name" value={form.values.name} onChange={form.handleChange} />
            </label>
          </div>
          <div>
            <label>
              Email:
              <input type="email" name="email" value={form.values.email} onChange={form.handleChange} />
            </label>
          </div>
          <button type="submit">Submit</button>
        </form>
      </header>
    </div>
  );
}

export default App;

Here, the useForm hook is used to manage the form state. The handleChange function updates the state when the input values change, and the resetForm function resets the form to its initial values when the form is submitted.

Run Your App: Save your changes and visit http://localhost:3000. You should see a simple form that logs the values to the console and resets when submitted.

Custom hooks are not limited to encapsulating state logic; they can share non-visual logic as well, such as data fetching, timers, or web socket connections.

Suppose you have multiple forms in your application that need to validate user input. Instead of duplicating the validation logic, you can create a custom hook to handle it.

Step-by-Step Guide

Create a Validation Hook: Inside the hooks folder, create a new file named useValidation.js.

Write the Hook Code: Open useValidation.js and write the following code:

function useValidation(initialValue, validate) {
  const [value, setValue] = useState(initialValue);
  const [error, setError] = useState('');

  const handleChange = (e) => {
    const newValue = e.target.value;
    setValue(newValue);
    setError(validate(newValue));
  };

  return {
    value,
    error,
    onChange: handleChange,
  };
}

export default useValidation;

This hook takes an initial value and a validation function. It returns the current value, an error message, and an onChange function to update the value and validate it.

Create a Validation Function: Create a new file named validators.js in the src folder and write the following code:

function isEmail(value) {
  const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
  return emailRegex.test(value) ? '' : 'Invalid email';
}

function minLength(min) {
  return (value) => value.length < min ? `Minimum length is ${min}` : '';
}

export { isEmail, minLength };

These functions validate whether a value is an email and whether it meets a minimum length requirement.

Use the Validation Hook in a Component: Open src/App.js and modify it to use the useValidation hook:

import React from 'react';
import useForm from './hooks/useForm';
import useValidation from './hooks/useValidation';
import { isEmail, minLength } from './validators';

function App() {
  const form = useForm({ name: '', email: '' });
  const nameValidation = useValidation(form.values.name, minLength(3));
  const emailValidation = useValidation(form.values.email, isEmail);

  const handleSubmit = (e) => {
    e.preventDefault();
    if (!nameValidation.error && !emailValidation.error) {
      console.log('Form submitted:', form.values);
      form.resetForm();
    } else {
      console.log('Validation errors');
    }
  };

  return (
    <div className="App">
      <header className="App-header">
        <form onSubmit={handleSubmit}>
          <div>
            <label>
              Name:
              <input
                type="text"
                name="name"
                value={form.values.name}
                onChange={(e) => {
                  form.handleChange(e);
                  nameValidation.onChange(e);
                }}
              />
              {nameValidation.error && <span>{nameValidation.error}</span>}
            </label>
          </div>
          <div>
            <label>
              Email:
              <input
                type="email"
                name="email"
                value={form.values.email}
                onChange={(e) => {
                  form.handleChange(e);
                  emailValidation.onChange(e);
                }}
              />
              {emailValidation.error && <span>{emailValidation.error}</span>}
            </label>
          </div>
          <button type="submit">Submit</button>
        </form>
      </header>
    </div>
  );
}

export default App;

Here, the useValidation hook is used to validate the name and email fields. Errors are displayed next to the input fields, and the form is only submitted if there are no validation errors.

Run Your App: Save your changes and visit http://localhost:3000. You should see a form with validation for the name and email fields.

Managing Side Effects

Using `useState` and `useEffect`

Many custom hooks will rely on useState and useEffect to manage state and side effects. Let’s create a custom hook that fetches data from an API when a component mounts.

Example: Creating a Hook for Data Fetching

Step-by-Step Guide

Create a New File for the Fetch Hook: Inside the hooks folder, create a new file named useFetch.js.

Write the Hook Code: Open useFetch.js and write the following code:

import { useState, useEffect } from 'react';

function useFetch(url) {
  const [data, setData] = useState(null);
  const [error, setError] = useState(null);
  const [loading, setLoading] = useState(true);

  useEffect(() => {
    fetch(url)
      .then(response => response.json())
      .then(data => {
        setData(data);
        setLoading(false);
      })
      +.catch(error => {
        setError(error);
        setLoading(false);
      });
  }, [url]);

  return { data, error, loading };
}

export default useFetch;

This hook fetches data from the provided URL when the component mounts. It returns the fetched data, any error that occurred, and a loading state to indicate whether the data is still being fetched.

Use the Fetch Hook in a Component: Open src/App.js and modify it to use the useFetch hook:

import React from 'react';
import useFetch from './hooks/useFetch';

function App() {
  const { data, error, loading } = useFetch('https://jsonplaceholder.typicode.com/posts/1');

  if (loading) return <div>Loading...</div>;
  if (error) return <div>Error: {error.message}</div>;

  return (
    <div className="App">
      <header className="App-header">
        <h1>Title: {data.title}</h1>
        <p>{data.body}</p>
      </header>
    </div>
  );
}

export default App;

Here, the useFetch hook is used to fetch data from a sample API. The component displays the fetched data, an error message if one occurs, and a loading message while the data is being fetched.

Run Your App: Save your changes and visit http://localhost:3000. You should see the fetched data displayed on the page.

Performance Optimization

Optimizing Component Performance with Custom Hooks

Custom hooks can also help optimize performance by encapsulating expensive operations or state management.

Example: Optimizing Expensive Calculations

Suppose you have a component that performs an expensive calculation whenever its input changes. You can encapsulate this logic in a custom hook to avoid performing the calculation on every render.

Step-by-Step Guide

Create a New File for the Calculation Hook: Inside the hooks folder, create a new file named useExpensiveCalculation.js.

Write the Hook Code: Open useExpensiveCalculation.js and write the following code:

import { useState, useEffect } from 'react';

function useExpensiveCalculation(value) {
  const [result, setResult] = useState(0);

  useEffect(() => {
    // Simulate an expensive calculation
    const result = expensiveCalculation(value);
    setResult(result);
  }, [value]);

  function expensiveCalculation(value) {
    // Simulate a delay to represent an expensive operation
    let result = 0;
    for (let i = 0; i < 1000000000; i++) {
      result += Math.sqrt(i);
    }
    return value * result;
  }

  return result;
}

export default useExpensiveCalculation;

This hook performs an expensive calculation whenever the input value changes. It uses useEffect to ensure the calculation is performed only when necessary.

Use the Calculation Hook in a Component: Open src/App.js and modify it to use the useExpensiveCalculation hook:

import React, { useState } from 'react';
import useExpensiveCalculation from './hooks/useExpensiveCalculation';

function App() {
  const [value, setValue] = useState(0);

  const result = useExpensiveCalculation(value);

  return (
    <div className="App">
      <header className="App-header">
        <div>
          <label>
            Value:
            <input type="number" value={value} onChange={(e) => setValue(e.target.value)} />
          </label>
        </div>
        <h1>Result: {result}</h1>
      </header>
    </div>
  );
}

export default App;

Here, the useExpensiveCalculation hook is used to perform the expensive calculation. The result is displayed in the component, and the calculation is only re-run when the input value changes.

Run Your App: Save your changes and visit http://localhost:3000. You should see an input field and a result display. The result is updated only when the input value changes.

Debugging Custom Hooks

Common Pitfalls

Debugging custom hooks can be challenging, especially when they involve asynchronous operations or complex state management. Here are some common pitfalls you should be aware of:

Invalid Hook Call Order: Hooks should always be called at the top level of the component or custom hook. Never call them inside loops, conditions, or nested functions.
Missing Dependencies in useEffect: When using useEffect inside a custom hook, always include all dependencies in the dependency array. Failing to do so can lead to bugs where the effect doesn’t run when it should.
Incorrect Return Values: Ensure that your custom hook returns the correct values and functions. This can help prevent mistakes and make the hook easier to use.

Debugging Techniques

Console Logging: The simplest way to debug a custom hook is to add console.log statements to track the flow and values of the hook. This can help you understand how the hook behaves over time.
React DevTools: Use React DevTools to inspect the state and props of your components. This can help you understand how the custom hook interacts with your components.
Unit Tests: Write unit tests for your custom hook to ensure it behaves as expected. You can use testing libraries like Jest and React Testing Library to write and run tests.

Testing Custom Hooks

Unit Testing

Testing custom hooks can be done using testing libraries like Jest and React Testing Library. Let’s write a simple unit test for the useCounter hook.

Step-by-Step Guide

Set Up Testing Library: Ensure that testing libraries are installed in your project. If not, you can install them using the following command:
```
npm install --save @testing-library/react @testing-library/jest-dom
```

Write a Test File: Create a new file named useCounter.test.js in the src folder and write the following code:

import { renderHook, act } from '@testing-library/react-hooks';
import useCounter from './hooks/useCounter';

test('should initialize with the provided initial value and step', () => {
  const { result } = renderHook(() => useCounter(5, 10));

  expect(result.current.count).toBe(5);
  expect(result.current.increment).toBeDefined();
  expect(result.current.decrement).toBeDefined();
  expect(result.current.reset).toBeDefined();
});

test('should increment and decrement the count by the provided step', () => {
  const { result } = renderHook(() => useCounter(0, 2));

  act(() => {
    result.current.increment();
  });
  expect(result.current.count).toBe(2);

  act(() => {
    result.current.decrement();
  });
  expect(result.current.count).toBe(0);
});

test('should reset the count to the initial value', () => {
  const { result } = renderHook(() => useCounter(1, 3));

  act(() => {
    result.current.increment();
    result.current.increment();
  });
  expect(result.current.count).toBe(7);

  act(() => {
    result.current.reset();
  });
  expect(result.current.count).toBe(1);
});

These tests verify that the useCounter hook initializes correctly, increments and decrements the count by the provided step, and resets the count to its initial value.

Run Your Tests: Open your terminal and run the following command to execute the tests:
```
npm test
```
You should see the test results in your terminal. The tests should pass if everything is set up correctly.

Integration Testing

Integration testing is another way to test custom hooks, especially when they involve side effects or multiple hooks. Let’s write an integration test for the useFetch hook.

Step-by-Step Guide

Create a Test File: Create a new file named useFetch.test.js in the src folder and write the following code:

import { renderHook, act, waitFor } from '@testing-library/react-hooks';
import useFetch from './hooks/useFetch';

// Mock the fetch function to simulate API responses
global.fetch = jest.fn(() =>
  Promise.resolve({
    json: () => Promise.resolve({ id: 1, title: 'Sample Post', body: 'Sample Body' }),
  })
);

test('should fetch data when the component mounts', async () => {
  const { result } = renderHook(() => useFetch('https://jsonplaceholder.typicode.com/posts/1'));

  await waitFor(() => expect(result.current.data).toBeDefined());

  expect(global.fetch).toHaveBeenCalledTimes(1);
  expect(global.fetch).toHaveBeenCalledWith('https://jsonplaceholder.typicode.com/posts/1');

  expect(result.current.data).toEqual({
    id: 1,
    title: 'Sample Post',
    body: 'Sample Body',
  });
});

test('should handle errors when fetching data', async () => {
  global.fetch.mockRejectedValue(new Error('Fetch failed'));

  const { result } = renderHook(() => useFetch('https://jsonplaceholder.typicode.com/posts/1'));

  await waitFor(() => expect(result.current.error).toBeDefined());

  expect(result.current.error.message).toBe('Fetch failed');
});

These tests use the @testing-library/react-hooks library to render and test the useFetch hook. They simulate fetching data and handle errors, ensuring that the hook behaves as expected in different scenarios.

Run Your Tests: Open your terminal and run the following command to execute the tests:
```
npm test
```
You should see the test results in your terminal. The tests should pass if everything is set up correctly.

Real-World Applications

Case Studies

Example: Building a Real-Time Chat Application

Custom hooks can greatly simplify the development of complex applications like real-time chat applications. Let’s create a custom hook that manages a chat connection using WebSockets.

Step-by-Step Guide

Create a New File for the Chat Hook: Inside the hooks folder, create a new file named useChat.js.

Write the Hook Code: Open useChat.js and write the following code:

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

function useChat(url) {
  const [messages, setMessages] = useState([]);
  const socketRef = useRef(null);

  useEffect(() => {
    socketRef.current = new WebSocket(url);

    socketRef.current.onmessage = (event) => {
      const message = JSON.parse(event.data);
      setMessages(prevMessages => [...prevMessages, message]);
    };

    socketRef.current.onclose = () => {
      socketRef.current.close();
    };

    return () => {
      socketRef.current.close();
    };
  }, [url]);

  const sendMessage = (message) => {
    if (socketRef.current.readyState === WebSocket.OPEN) {
      socketRef.current.send(JSON.stringify(message));
    }
  };

  return {
    messages,
    sendMessage,
  };
}

export default useChat;

This hook opens a WebSocket connection to the provided URL, receives messages, and sends messages. It also handles the connection lifecycle.

Use the Chat Hook in a Component: Open src/App.js and modify it to use the useChat hook:

import React, { useState } from 'react';
import useChat from './hooks/useChat';

function App() {
  const [message, setMessage] = useState('');
  const chat = useChat('ws://example.com/socket');

  const handleSubmit = (e) => {
    e.preventDefault();
    chat.sendMessage(message);
    setMessage('');
  };

  return (
    <div className="App">
      <header className="App-header">
        <h1>Chat</h1>
        <ul>
          {chat.messages.map((msg, index) => (
            <li key={index}>{msg.text}</li>
          ))}
        </ul>
        <form onSubmit={handleSubmit}>
          <input value={message} onChange={(e) => setMessage(e.target.value)} />
          <button type="submit">Send</button>
        </form>
      </header>
    </div>
  );
}

export default App;

Here, the useChat hook manages the chat connection and message handling. The App component displays the messages and allows the user to send new messages.

Run Your App: Save your changes and visit http://localhost:3000. You should see a simple chat interface that displays messages and allows the user to send new messages.

Summary and Next Steps

Recap of Key Points

Custom hooks are a powerful feature in React that allow you to reuse logic between components.
They follow a simple structure and naming convention.
You can encapsulate state logic, non-visual logic, and side effects using custom hooks.
Best practices include reusing logic, naming hooks correctly, and following the Rules of Hooks.
Testing custom hooks with unit and integration tests ensures they work as expected.

Resources for Further Learning

Official React Custom Hooks Documentation
React Testing Library
Hook Flow - A tool to visualize the state and effects of React hooks.
Awesome React Hooks - A curated list of custom hooks for React.

By mastering custom hooks, you can write more modular, reusable, and maintainable code. Custom hooks are an essential tool in the React toolkit, and understanding them can greatly enhance your development experience.

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React Router Navigation

Styling In React

State Management with Hooks

Hooks Performance Optimization

Working With Apis In React

React Advanced Concepts

Additional Concepts

Custom Hooks in React

Introduction to Custom Hooks

What is a Custom Hook?

Why Use Custom Hooks?

Getting Started with Custom Hooks

Setting Up Your Development Environment

Basic Structure of a Custom Hook

Writing Your First Custom Hook

Creating a Basic Custom Hook

Step-by-Step Guide

Example: Creating a Counter Hook

Step-by-Step Guide

Best Practices for Custom Hooks

Reusing Logic with Hooks

Step-by-Step Guide

Naming Custom Hooks

Guidelines for Custom Hooks

Advanced Topics

Encapsulating State Logic

Example: Encapsulating Form State Logic

Step-by-Step Guide

Sharing Non-Visual Logic

Example: Sharing Logic Between Forms

Step-by-Step Guide

Managing Side Effects

Using useState and useEffect

Example: Creating a Hook for Data Fetching

Step-by-Step Guide

Performance Optimization

Optimizing Component Performance with Custom Hooks

Example: Optimizing Expensive Calculations

Step-by-Step Guide

Debugging Custom Hooks

Common Pitfalls

Debugging Techniques

Testing Custom Hooks

Unit Testing

Step-by-Step Guide

Integration Testing

Step-by-Step Guide

Real-World Applications

Case Studies

Example: Building a Real-Time Chat Application

Step-by-Step Guide

Summary and Next Steps

Recap of Key Points

Resources for Further Learning

On this page

Using `useState` and `useEffect`