Javascript/Event Loop
Javascript / Topic

Event Loop

Understand how JavaScript handles asynchronous operations using the Call Stack, Web APIs, Callback Queue, Microtask Queue, and Event Loop.

Difficulty

Intermediate

Read time

20 min

Format

Concept + Code

Focus

Interview ready
Concepts
Event Loop
Call Stack
Microtask
Async

01 / Foundation

Understand the concept

JavaScript is single-threaded, meaning it executes one piece of code at a time. The Event Loop enables asynchronous behavior without creating additional JavaScript threads.

Understanding the Event Loop is essential for mastering Promises, async/await, timers, and browser performance.

02 / Implementation

Execution Order Example

event-loop.js
console.log("Start");

setTimeout(() => {
  console.log("Timeout");
}, 0);

Promise.resolve().then(() => {
  console.log("Promise");
});

console.log("End");

// Output:
// Start
// End
// Promise
// Timeout

04 / Interview

Test your understanding