Stop 02 · Node.js FundamentalsTopics · 3/18

Event Loop

In short

The mechanism that lets single-threaded Node.js handle thousands of concurrent connections by delegating I/O work and processing callbacks as they complete, instead of blocking.

How to learn this

1Log the order of `setTimeout`, `Promise.then` and synchronous code to see the event loop phases.
2Learn the difference between the microtask queue (Promises) and macrotask queue (setTimeout).
3Understand why a long synchronous computation blocks the entire event loop.

More topics at this stop

Node.js Runtime V8 Engine Non-Blocking I/O Modules (CommonJS vs ESM)NPM & Package Management package.json Async Programming Callbacks Promises Async/Await Streams Buffers File System (fs)Process & Environment Variables Event Emitter Child Processes Clustering

Stuck on this topic? Ask an Insider

Get 1:1 guidance from people who've walked this exact path — on the InsideEdge app.

Download