5 Mistakes made by Node.js Beginners — Part 1

In this series, we’ll look into the common mistakes made by Node.js beginners. This is the part 1, where we’ll look at the first 5 mistakes.

The other parts are:

• Part 2 (Mistakes 6to 10)
• Part 3 (Mistakes 11 to 15)

Mistake 1 — Blocking the event loop

This is undoubtedly the top mistake. The event loop is a crucial component responsible for handling asynchronous operations. It is the mechanism that allows Node.js to be non-blocking and efficiently handle multiple concurrent requests. However, beginner Node.js developers may inadvertently write code that blocks the event loop, leading to performance issues.

The event loop in Node.js operates by continuously checking for new events and executing their corresponding callbacks. When a callback is executed, it should complete quickly and return control back to the event loop. If a callback takes a long time to execute, it can block the event loop, preventing other incoming requests from being processed in a timely manner.

For example, consider the following code:

app.get('/blocking', (req, res) => {
  let sum = 0;
  for (let i = 0; i < 1000000000; i++) {
    sum += i;
  }
  res.send(`The sum is ${sum}`);
});

In this scenario, the /blocking endpoint performs a long-running calculation, which blocks the event loop. As a result, any subsequent requests to the server will be delayed until the calculation is complete, leading to a poor user experience and decreased application responsiveness.

To avoid blocking the event loop, beginner Node.js developers should learn to leverage asynchronous programming techniques, such as using non-blocking I/O operations, offloading CPU-intensive tasks to worker threads or a separate process, and using the setImmediate() or process.nextTick() functions to ensure that the event loop is not blocked.

By understanding and addressing the issue of blocking the event loop, beginner Node.js developers can improve the performance and scalability of their applications.

Mistake 2 — Improper error handling

Error handling is a critical aspect of every language, not just Node.js. A proper error handling ensures that applications can gracefully handle and recover from unexpected situations. Beginner Node.js developers often struggle with implementing proper error-handling mechanisms, which can lead to unpredictable behavior and crashes in their applications.

In Node.js, errors can occur in various forms, such as synchronous exceptions, asynchronous errors, or errors generated by third-party libraries. Beginner developers may not fully understand how to handle these different types of errors effectively.

Let’s look at the following code:

app.get('/error', (req, res) => {
  try {
    throw new Error('An error occurred');
  } catch (err) {
    console.error(err);
    res.status(500).send('An error occurred');
  }
});

In this example, the try-catch block is used to handle a synchronous error. However, this approach is not sufficient for handling asynchronous errors, as the try-catch block will not capture errors that occur in asynchronous callbacks, such as those used in database queries or HTTP requests.

To properly handle asynchronous errors, beginner Node.js developers should learn to use error-first callbacks, where the first argument of a callback is reserved for an error object. They should also learn to use promises and the async/await syntax, which provide a more intuitive way of handling asynchronous errors.

Additionally, beginner developers should understand the importance of propagating errors up the call stack, ensuring that errors are handled at the appropriate level of the application. This can be achieved by using built-in error-handling mechanisms, such as the process.on('uncaughtException') and process.on('unhandledRejection') events.

By mastering proper error handling, beginner Node.js developers can ensure that their applications are more robust, maintainable, and able to provide a better user experience by gracefully handling and recovering from errors.

Mistake 3 — Inefficient database interactions

When building Node.js applications, beginner developers often struggle with optimizing their interactions with databases, leading to performance issues and inefficient data retrieval.

One common mistake made by beginner Node.js developers is the lack of proper optimization of database queries. They may write queries that retrieve more data than necessary or perform unnecessary joins, resulting in slow response times and increased resource consumption.

For example, consider the following code:

app.get('/users', async (req, res) => {
  const users = await User.find({}, '-_id name email');
  res.json(users);
});

In this example, the User.find() query retrieves all users, including fields that may not be necessary for the current use case. This can lead to performance issues, especially as the number of users in the database grows.

To optimize database interactions, beginner Node.js developers should learn techniques such as:

1. Pagination: Implement pagination to retrieve data in smaller chunks, reducing the load on the database and the network.
2. Indexing: Create appropriate indexes on the database fields used in queries to speed up data retrieval.
3. Selective field retrieval: Only retrieve the necessary fields from the database, rather than fetching all fields.
4. Asynchronous database operations: Use asynchronous database operations, such as promises or async/await, to avoid blocking the event loop.
5. Query optimization: Analyze and optimize complex database queries to ensure efficient data retrieval.

By mastering these techniques, beginner Node.js developers can improve the performance and scalability of their applications, ensuring that database interactions do not become a bottleneck.

Mistake 4 — Lack of modularization

Modularization is a fundamental principle in software development that helps to create maintainable, scalable, and organized applications. Beginner Node.js developers often struggle with properly modularizing their code, leading to monolithic and hard-to-manage applications.

In the context of Node.js, modularization involves breaking down an application into smaller, reusable components or modules. Each module should have a well-defined responsibility and interface, making the codebase more organized and easier to understand, maintain, and extend.

Consider the following example of a poorly modularized Node.js application:

app.js

const express = require('express');
const app = express();

// All application logic in a single file
app.get('/users', (req, res) => {
  // Fetch users from database
  const users = [
    { id: 1, name: 'John Doe', email: 'john@example.com' },
    { id: 2, name: 'Jane Smith', email: 'jane@example.com' },
  ];
  res.json(users);
});

app.post('/users', (req, res) => {
  // Add new user to database
  const newUser = { id: 3, name: 'Bob Johnson', email: 'bob@example.com' };
  res.status(201).json(newUser);
});

app.listen(3000, () => {
  console.log('Server started on port 3000');
});

In this example, all the application logic is contained within a single file, app.js. This approach can quickly become unwieldy as the application grows in complexity, making it difficult to maintain and scale.

To address this issue, beginner Node.js developers should learn to modularize their applications by separating concerns into distinct modules. This could involve creating separate modules for handling routing, database interactions, and business logic.

Here’s an example of a more modularized approach:

app.js

// app.js
const express = require('express');
const app = express();
const userRouter = require('./routes/userRouter');

app.use('/users', userRouter);

app.listen(3000, () => {
  console.log('Server started on port 3000');
});

routes/userRouter.js

const express = require('express');
const router = express.Router();
const userController = require('../controllers/userController');

router.get('/', userController.getUsers);
router.post('/', userController.createUser);

module.exports = router;

// controllers/userController.js
const userService = require('../services/userService');

exports.getUsers = async (req, res) => {
  const users = await userService.getUsers();
  res.json(users);
};

exports.createUser = async (req, res) => {
  const newUser = await userService.createUser(req.body);
  res.status(201).json(newUser);
};

services/userService.js

exports.getUsers = async () => {
  // Fetch users from database
  return [
    { id: 1, name: 'John Doe', email: 'john@example.com' },
    { id: 2, name: 'Jane Smith', email: 'jane@example.com' },
  ];
};

exports.createUser = async (userData) => {
  // Add new user to database
  return { id: 3, name: 'Bob Johnson', email: 'bob@example.com' };
};

In this modularized approach, the application logic is divided into separate modules, each with a well-defined responsibility. This makes the codebase more organized, maintainable, and easier to scale as the application grows.

Mistake 5 — Inadequate testing

Once again, a common mistake, not very specific to Node.js.

Testing is a crucial aspect that ensures the reliability, correctness, and maintainability of applications. Beginner Node.js developers often overlook or underestimate the importance of writing tests, leading to applications with bugs, regressions, and decreased developer productivity.

In the world of Node.js development, there are several types of tests that beginner developers should learn to implement, including:

1. Unit Tests: These tests focus on verifying the correctness of individual units of code, such as functions or modules, in isolation.
2. Integration tests: These tests evaluate how different components of the application work together, ensuring the integration and communication between them.
3. End-to-End (E2E) tests: These tests simulate the entire user journey, testing the application from the user’s perspective and ensuring that the application behaves as expected.

Consider the following example of a simple Node.js application:

// calculator.js
exports.add = (a, b) => {
  return a + b;
};

exports.subtract = (a, b) => {
  return a - b;
};

A beginner Node.js developer may neglect to write tests for this application, leaving it vulnerable to bugs and regressions. However, by implementing unit tests, the developer can ensure the correctness of the individual functions:

// calculator.test.js
const { add, subtract } = require('./calculator');

test('add function', () => {
  expect(add(2, 3)).toBe(5);
  expect(add(-1, 1)).toBe(0);
});

test('subtract function', () => {
  expect(subtract(5, 3)).toBe(2);
  expect(subtract(10, 4)).toBe(6);
});

By writing these unit tests, the developer can catch any issues with the add and subtract functions early in the development process, making the application more robust and easier to maintain.

In addition to unit tests, beginner Node.js developers should also learn to write integration and E2E tests to ensure the overall functionality and behavior of their applications. This can be achieved using testing frameworks like Mocha, Chai, and Puppeteer.

That’s all about it. I hope this has been of help to you as a beginner Node developer.

The other parts are:

• Part 2 (Mistakes 6 to 10)
• Part 3 (Mistakes 11 to 15)