Technical Lesson: Refactoring API Calls with Custom Hooks and npm Package Management

Task 1: Define the Problem

In React applications, fetching data from an API is a common task. However, when multiple components need to fetch different data, they often duplicate the same logic, leading to code that is:

• Difficult to maintain ❌ -- Updates need to be made in multiple places.
• Repetitive ❌ -- Similar useEffect logic is used across components.
• Error-prone ❌ -- Debugging network requests becomes harder.

Task 2: Determine the Design

To fix this, we will:

1. Refactor API calls into a Custom Hook (useFetchData.js) to centralize logic.
2. Use npm to manage dependencies and install third-party packages.
3. Introduce Chalk for better logging -- Adding color-coded debugging messages to track API calls in the browser console.

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Task 3: Develop, Test, and Refine the Code

Step 1: Fork, Clone, and Run the Application

Fork this repo , then open in VSCode:

# Create a new Vite project
git clone <link to your forked repo>

# Navigate into the project folder and open in VSCode
cd custom-hooks-technical lesson
code .

# Install necessary dependencies
npm install

# Start the development server
npm run dev

Step 2: Install Additional Dependencies

To enhance debugging and logging, install the following:

npm install chalk

Why use Chalk?

• ✅ Enhances debugging -- Color-coded logs help identify success, errors, and warnings.
• ✅ Improves readability -- Makes console output clearer when fetching API data.

Step 3: Evaluate Current Code

Scenario: Why Use a Custom Hook?

❌ BEFORE (Without a Custom Hook - Current State)

Right now, both Posts.jsx and Users.jsx fetch data separately. Each uses useEffect with duplicated API-fetching logic.

Code for Posts.jsx (before refactoring)

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

function Posts() {
  const [posts, setPosts] = useState([]);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState(null);

  useEffect(() => {
    fetch("https://jsonplaceholder.typicode.com/posts")
      .then((res) => {
        if (!res.ok) {
          throw new Error("Failed to fetch posts");
        }
        return res.json();
      })
      .then((data) => {
        setPosts(data);
        setLoading(false);
      })
      .catch((err) => {
        setError(err.message);
        setLoading(false);
      });
  }, []);

  if (loading) return <p className="loading">Loading posts...</p>;
  if (error) return <p className="error">Error: {error}</p>;

  return (
    <div className="container">
      <h2>Posts</h2>
      <ul>
        {posts.map((post) => (
          <li key={post.id}>{post.title}</li>
        ))}
      </ul>
    </div>
  );
}

export default Posts;

Code for Users.jsx (before refactoring)

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

function Users() {
  const [users, setUsers] = useState([]);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState(null);

  useEffect(() => {
    fetch("https://jsonplaceholder.typicode.com/users")
      .then((res) => {
        if (!res.ok) {
          throw new Error("Failed to fetch users");
        }
        return res.json();
      })
      .then((data) => {
        setUsers(data);
        setLoading(false);
      })
      .catch((err) => {
        setError(err.message);
        setLoading(false);
      });
  }, []);

  if (loading) return <p className="loading">Loading users...</p>;
  if (error) return <p className="error">Error: {error}</p>;

  return (
    <div className="container">
      <h2>Users</h2>
      <ul>
        {users.map((user) => (
          <li key={user.id}>{user.name}</li>
        ))}
      </ul>
    </div>
  );
}

export default Users;

Step 4: Add a New File for the Custom Hook

Create a new file inside src/hooks/ called useFetchData.js.

📁 File: src/hooks/useFetchData.js

import { useState, useEffect } from "react";
import chalk from "chalk";

/**
 * Custom Hook for fetching API data.
 * @param {string} url - The API endpoint.
 * @param {Object} options - Optional fetch settings.
 * @returns {Object} { data, loading, error, refetch }
 */
function useFetchData(url, options = {}) {
  const [data, setData] = useState(null);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState(null);

  // Fetch function that can be triggered manually
  const fetchData = async () => {
    setLoading(true);
    console.log(chalk.blue(`Fetching data from: ${url}`));

    try {
      const response = await fetch(url, options);
      if (!response.ok) throw new Error("Failed to fetch data");

      const result = await response.json();
      console.log(chalk.green("Data fetched successfully!"), result);
      setData(result);
    } catch (err) {
      console.log(chalk.red("Error fetching data:"), err.message);
      setError(err.message);
    } finally {
      setLoading(false);
    }
  };

  // Fetch data on component mount
  useEffect(() => {
    fetchData();
  }, [url]);

  return { data, loading, error, refetch: fetchData };
}

export default useFetchData;

✅ Improvements:

• Encapsulates API logic -- No need to write useEffect in every component.
• Reusability -- Works in any component needing API data.
• Refetch function -- Allows manual data fetching with a button click.
• Uses Chalk -- Adds color-coded console logs for easier debugging.

Step 5: Refactor Posts.jsx to Use Custom Hook

📁 File: src/components/Posts.jsx

import React from "react";
import useFetchData from "../hooks/useFetchData";

function Posts() {
  const { data, loading, error, refetch } = useFetchData(
    "https://jsonplaceholder.typicode.com/posts"
  );

  if (loading) return <p className="loading">Loading posts...</p>;
  if (error) return <p className="error">Error: {error}</p>;

  return (
    <div className="container">
      <h2>Posts</h2>
      <button onClick={refetch}>Refresh Posts</button>
      <ul>
        {data.map((post) => (
          <li key={post.id}>{post.title}</li>
        ))}
      </ul>
    </div>
  );
}

export default Posts;

✅ Refactored Features:

• Uses useFetchData instead of duplicating logic.
• Includes a "Refresh" button to manually re-fetch posts.
• Chalk logs API requests and errors.

Step 6: Refactor Users.jsx to Use Custom Hook

Now, let's replace the old useEffect logic in Users.jsx with our Custom Hook (useFetchData).

📁 File: src/components/Users.jsx

import React from "react";
import useFetchData from "../hooks/useFetchData";

function Users() {
  const { data, loading, error, refetch } = useFetchData(
    "https://jsonplaceholder.typicode.com/users"
  );

  if (loading) return <p className="loading">Loading users...</p>;
  if (error) return <p className="error">Error: {error}</p>;

  return (
    <div className="container">
      <h2>Users</h2>
      <button onClick={refetch}>Refresh Users</button>
      <ul>
        {data.map((user) => (
          <li key={user.id}>{user.name}</li>
        ))}
      </ul>
    </div>
  );
}

export default Users;

✅ Refactored Features in Users.jsx:

• Uses useFetchData to remove redundant useEffect logic.
• Includes a "Refresh Users" button to manually re-fetch users.
• Improved readability and maintainability.

Step 7: View Installed Dependencies and Vulnerabilities

To list all installed packages:

npm list --depth=0

Checking for Security Vulnerabilities
To scan the project for security vulnerabilities in dependencies, run:

npm audit

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Task 5: Document and Maintain

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Using Git Best Practices

To track changes efficiently, follow this Git workflow:

1. Create a new feature branch:

git checkout -b feature-custom-hook

2. Stage and commit changes:

git add .
git commit -m "Added useFetchData custom hook and npm dependency management"

3. Push the branch to GitHub:

git push origin feature-custom-hook

4. ** Create a pull request (PR) on GitHub and merge into main
5. ** After merging, delete the feature branch locally:**

git branch -d feature-custom-hook

Final Considerations

✅ Why Use Custom Hooks?

• Modular Code: Extracts logic into reusable functions.
• Easier Maintenance: Updates apply to all components using the hook.
• Less Repetition: No need to write useEffect API calls in every component.

✅ Why Use npm for Package Management?

• Dependency Tracking: Manages third-party libraries efficiently.
• Security Updates: Detects and fixes vulnerabilities.
• Version Control: Ensures compatibility across different project setups.

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Summary

By completing this lesson, students have: ✅ Created a Custom Hook (useFetchData) for API fetching.
✅ Used the Custom Hook in multiple components (Posts.jsx, Users.jsx).
✅ Removed duplicate useEffect logic, making the code more modular.
✅ Installed and used Chalk to log API requests.
✅ Followed npm best practices for package management.