Chapter 28: Database Transactions in JavaScript

BEGIN, COMMIT, ROLLBACK for data integrity. In this chapter, you will learn database transactions in depth with JavaScript code examples, explanations, and best practices.

Overview

This chapter covers database transactions for Kungfu.js developers using JavaScript. We will start with the basics, move through practical examples, and end with advanced techniques and common pitfalls.

Why This Matters

Understanding database transactions is essential because it is a core part of building web applications. Every real-world app needs to handle begin, commit, rollback for data integrity. Skipping this chapter would leave a gap in your knowledge that would cause problems later.

Code Example

Here is how to work with databases in JavaScript:

db.transaction(|tx| async move {
    tx.execute(
        "INSERT INTO users (email) VALUES ($1)",
        &[json!("alice@example.com")]
    ).await?;
    
    tx.execute(
        "INSERT INTO logs (msg) VALUES ($1)",
        &[json!("user created")]
    ).await?;
    
    Ok(())  // commits
}).await?;  // if this returns Err, ROLLBACK is automatic

How the ORM Works

The Kungfu.js ORM uses parameterized queries. This means user input never gets interpolated into SQL strings. Instead, placeholders like $1, $2 are used, and the actual values are passed separately. This makes SQL injection impossible.

For example, if you search for a user by email, the ORM generates: SELECT * FROM users WHERE email = $1 and passes the email value as a parameter. Even if the email contains SQL code like ' OR 1=1 --, it is treated as a plain string, not as SQL.

Common Mistakes

• Not reading the documentation: Always check the API reference when something does not work as expected.
• Skipping security: Never disable the default middleware unless you have a very good reason. Security is not optional.
• Not testing: Write tests for your handlers. Kungfu.js makes this easy with the built-in test utilities.

Summary

In this chapter, you learned about database transactions in JavaScript. You saw code examples, understood how things work under the hood, and learned about common mistakes to avoid.

What is Next?

In chapter 29, we will cover Database Migrations: Generate and apply schema changes.