Murray  Beatty

Murray Beatty

1594634799

Understanding JavaScript Call Stack, Task Queue and Event Loop

Disclaimer: This article is heavily inspired by a conference talk given by Phillip Roberts in EUConf 2014.

One thing critics of JS like to point out is that it is single threaded. When I started coding in JS, this confused me. Then how did JS handle async functions? How can we have things like setTimeout() that seems to work independently from the main thread? Hopefully by the end of the article, you will have answers to all these questions. Another goal of this article is to explain some core advanced concepts of JS: the call stack, the task queue and the event loop, which are fundamental to understanding how JS works within the browser.


Let’s say you wrote some JS code for a web app and shipped it. That JS code is run on the browser. How does the browser know what to do with it? The browser is able to run the JS code because it has a JS engine, which for Chrome is the V8 JavaScript engine. In simple terms, V8 knows how to convert JS code into machine code.

The browser is not just the JavaScript engine. It has its own set of APIs, called the Web APIs. setTimeout() is a part of this set of APIs. When you invoke functions such as setTimeout(), you are using an API function that the browser has exposed to you.

The browser is able to run the JS code because it has a JS engine, which for Chrome is the V8 JavaScript engine.

#software-engineering #programming #front-end-development #javascript #js

What is GEEK

Buddha Community

Understanding JavaScript Call Stack, Task Queue and Event Loop
Gordon  Taylor

Gordon Taylor

1624969920

How Javascript Is Single Threaded? in-Depth Explaination Of Event Loop and Call Stacks

I started learning Javascript about 2 years ago and wondering to find bits and pieces to explore how it internally works. I’d gotta heard words like v8 runtime engine which runs on browser but didn’t know anything about it and started doing my own research and experiment in the browser. Mostly all JS dev might have heard the term V8, chrome’s Runtime but some might even didn’t really know what that meant, what that did.

First of all, what is Javascript under the hood — the core component of NodeJS. Well, JS is single threaded, single concurrent language which has a call stack, an event loop, a callback queue and some other APIs. If we talk about the v8 runtime in the browser, the below one is simplified view of what it really is…

What is call stack?

You can think call stack to be a functional stack or execution stack when your Javascript code is run line by line. Unless the part of code is handed over to the callback queue, it fills the call stack of a run-time engine.

Consider the following image for the sake of understanding.

Here, first of all JS is designed to be run on the main() thread and so the main() function will be called first when we execute the above code all together. The entry execution point is console.log() statement and the execution will be halted until the argument provided inside does not finish its execution i.e. bar(6). Now, the bar(6) will be pushed on to the stack and then it calls the function foo(3*6) and hence comes on top. Now, when the execution of foo() finishes, it will return the result by popping the entry from stack and comes down to bar(6) which in turn will return entry to the console and it prints the result.

#javascript #event-loop #call-stack #web-development

Lowa Alice

Lowa Alice

1624406400

JavaScript Loops Tutorial

JavaScript loops made simple.

📺 The video in this post was made by Programming with Mosh
The origin of the article: https://www.youtube.com/watch?v=s9wW2PpJsmQ&list=PLTjRvDozrdlxEIuOBZkMAK5uiqp8rHUax&index=8
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Thanks for visiting and watching! Please don’t forget to leave a like, comment and share!

#javascript #loops #javascript loops #javascript loops tutorial

Hertha  Mayer

Hertha Mayer

1595334123

Authentication In MEAN Stack - A Quick Guide

I consider myself an active StackOverflow user, despite my activity tends to vary depending on my daily workload. I enjoy answering questions with angular tag and I always try to create some working example to prove correctness of my answers.

To create angular demo I usually use either plunker or stackblitz or even jsfiddle. I like all of them but when I run into some errors I want to have a little bit more usable tool to undestand what’s going on.

Many people who ask questions on stackoverflow don’t want to isolate the problem and prepare minimal reproduction so they usually post all code to their questions on SO. They also tend to be not accurate and make a lot of mistakes in template syntax. To not waste a lot of time investigating where the error comes from I tried to create a tool that will help me to quickly find what causes the problem.

Angular demo runner
Online angular editor for building demo.
ng-run.com
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Let me show what I mean…

Template parser errors#

There are template parser errors that can be easy catched by stackblitz

It gives me some information but I want the error to be highlighted

#mean stack #angular 6 passport authentication #authentication in mean stack #full stack authentication #mean stack example application #mean stack login and registration angular 8 #mean stack login and registration angular 9 #mean stack tutorial #mean stack tutorial 2019 #passport.js

Eldora  Bradtke

Eldora Bradtke

1594449120

Understanding JavaScript Call Stack, Task Queue and Event Loop

One thing critics of JS like to point out is that it is single threaded. When I started coding in JS, this confused me. Then how did JS handle async functions? How can we have things like setTimeout() that seems to work independently from the main thread? Hopefully by the end of the article, you will have answers to all these questions. Another goal of this article is to explain some core advanced concepts of JS: the call stack, the task queue and the event loop, which are fundamental to understanding how JS works within the browser.


Let’s say you wrote some JS code for a web app and shipped it. That JS code is run on the browser. How does the browser know what to do with it? The browser is able to run the JS code because it has a JS engine, which for Chrome is the V8 JavaScript engine. In simple terms, V8 knows how to convert JS code into machine code.

The browser is not just the JavaScript engine. It has its own set of APIs, called the Web APIs. setTimeout() is a part of this set of APIs. When you invoke functions such as setTimeout(), you are using an API function that the browser has exposed to you.

The browser is able to run the JS code because it has a JS engine, which for Chrome is the V8 JavaScript engine.

#software-engineering #front-end-development #javascript #js #programming

Murray  Beatty

Murray Beatty

1594634799

Understanding JavaScript Call Stack, Task Queue and Event Loop

Disclaimer: This article is heavily inspired by a conference talk given by Phillip Roberts in EUConf 2014.

One thing critics of JS like to point out is that it is single threaded. When I started coding in JS, this confused me. Then how did JS handle async functions? How can we have things like setTimeout() that seems to work independently from the main thread? Hopefully by the end of the article, you will have answers to all these questions. Another goal of this article is to explain some core advanced concepts of JS: the call stack, the task queue and the event loop, which are fundamental to understanding how JS works within the browser.


Let’s say you wrote some JS code for a web app and shipped it. That JS code is run on the browser. How does the browser know what to do with it? The browser is able to run the JS code because it has a JS engine, which for Chrome is the V8 JavaScript engine. In simple terms, V8 knows how to convert JS code into machine code.

The browser is not just the JavaScript engine. It has its own set of APIs, called the Web APIs. setTimeout() is a part of this set of APIs. When you invoke functions such as setTimeout(), you are using an API function that the browser has exposed to you.

The browser is able to run the JS code because it has a JS engine, which for Chrome is the V8 JavaScript engine.

#software-engineering #programming #front-end-development #javascript #js