Why Is JavaScript Single-Threaded?

JavaScript was created in just ten days with a single goal in mind: to make a simple scripting language for the web. Given the rapid development and the constraints of the time, sticking with a single-threaded model was the smartest choice.

Why single-threaded? Well, it meant that developers didn’t have to wrestle with complex issues like race conditions or deadlocks that are common in multi-threaded environments. For the early web, where many developers were just getting started, this simplicity was crucial.

At that time, web browsers weren’t built for handling complex, multi-threaded tasks. A single-threaded JavaScript model was not only practical but also efficient. It made it easy for JavaScript to interact with the Document Object Model (DOM) and manage user events seamlessly, keeping things straightforward and smooth.

I have created a set of resources for learning asynchronous JavaScript. These guides—Callbacks, Promises, and Async/Await —cover everything I’ve learned from years of real-world JavaScript experience.

If you found this article helpful, you’ll get so much out of these guides. Each one is optimized for those “lightbulb moments,” building a strong mental model for how asynchronous JavaScript works and how you can use it to create fast, dynamic applications.