Summary
This chapter explains how JavaScript handles asynchronous operations like setTimeout in a non-blocking fashion by scheduling callbacks to run later while the main code continues executing.

General domain of usage
Backend development


JavaScript does not always execute code step by step from top to bottom.

Some operations take time, such as reading data, making requests, or waiting for a response. JavaScript handles these operations asynchronously, which means it does not block the rest of the code while waiting.

```javascript
console.log("Start");

setTimeout(() => {
  console.log("Done");
}, 1000);

console.log("End");
```

Even though the timeout is written in the middle, the output will be:
```
Start
End
Done
```
This happens because the delayed operation runs later, while the rest of the code continues immediately.

This behavior is important in backend development because many tasks involve waiting, such as database queries or API calls.


Learn the core concepts of JavaScript needed for backend development, including variables, data structures, functions, and asynchronous code. Practice working with real data and understand how JavaScript behaves outside the browser. Build a strong foundation before moving on to Node.js and server-side development.

Understanding Asynchronous JavaScript