Careeroza

Asynchronous Code

Do Not Wait

Asynchronous code starts a task (timer, network request, file read) and continues immediately. The result is handled later by a callback, promise or await.

Example

Notice that "End" prints before the timeout, even with a 0 ms delay.

console.log('Start');
setTimeout(() => console.log('Timeout finished'), 0);
console.log('End');

Output

Start
End
Timeout finished

Sync vs Async

	Synchronous	Asynchronous
Execution	in order, one after another	starts now, finishes later
Blocks the thread	yes	no
Examples	loops, math, array methods	fetch, setTimeout, file/DB access
Handled with	normal code	callbacks, promises, async/await