Systems | Development | Analytics | API | Testing

Today, we’re releasing the JavaScript SDK with full TypeScript support for Koyeb Sandboxes. Less than a month ago, we introduced Koyeb Sandboxes and our Python SDK, giving teams a simple way to run AI-generated code securely in isolated environments. The JavaScript SDK expands this experience and brings the same secure, high-performance sandboxes directly to JavaScript/TypeScript applications, so developers can run AI-generated and untrusted code safely without managing infrastructure.

Whether for frontend or backend, testing is a key aspect of building trustworthy JavaScript applications. For example, when writing code that relies on external modules or services such as APIs, databases, or configuration providers, mocking can allow for a more isolated testing structure without those real dependencies. If you are using Jest, one of the most popular JavaScript testing frameworks, then you may have seen the term mock.

When I first started building websites in 2021, the decision to use JavaScript was an easy one – it was strong, well-documented, had a good community and seemed straightforward. I can recall many late nights debugging runtime errors that could’ve easily been picked up at compile-time, grappling with type coercion, and losing my mind trying to make consistent decisions in with large and growing code bases.

The filter method on a JavaScript array is one of the most powerful and widely used of all the array methods available for data manipulation. Whether it be filtering out unwanted elements, working your way through a number of datasets, or performing cleanup on an array, the filter method will give you a very elegant solution to each of those problems and any developer must know how to use it.

Ask any JavaScript developer their most used debugging tool and chances are the answer will be console.log. It’s immediate, low friction, and available in every browser. For development, it’s fantastic. But for production and complex applications, if you rely on console.log alone, cracks begin to show. It lacks context, doesn’t persist, and makes reproducing or analyzing user-reported issues a challenge. In this article, we’ll look at smarter, scalable debugging strategies.

Node.js is known for its non-blocking, event-driven architecture, making it great for handling I/O-bound tasks like web requests and file operations. But when it comes to CPU-intensive tasks, things get tricky. Because Node.js runs JavaScript in a single-threaded environment, heavy computations can block the event loop and degrade application performance. That’s where Worker Threads come in.