This is true but i think its important to not call event queue "stack" when the real data structure its a Queue. When you think about stacks and queues from real life everything makes sense
Finally, after looking for n^1000 videos, forums... I found a person who can explain these terms in real simple and understandable way 😭really appreciate your work man.
I've been developing in JavaScript for over 20 years now. But when I was interviewed recently for a new job, and asked about JavaScript event loop, I could not remember it for the life of me. This is mainly academical knowledge, not something that you need as an experienced developer. People who do interview are often dumb, and do not understand that.
...this video explains it poorly actually. and you do need to know it.. you're wrong. not knowing event loop and execution context and enviorement and the phases.. is how people fck themsealves with accidental closures and other stuff... most important part to know about event loop is about task queue and microtask queue, how microtask queue has priority, and that web apis.. some of them are callback based, some of them are promise based .. even setTimeout 1000ms for example.. is not 100% guaranteed,that it actually is 1000ms , that's not execution to time.. that's execution to enqueue of microtask queue.
i am really thankful for this video just before my interview, , feel having clear idea about what happen behind the scenes with node.js, please more advanced topics like this with such great explanantion
Hi , i was trying to wrap my head around the event loop, one suggestion for the video , a brief about v8 + libUv must have been wonderful specially mentioning about the 4 extra threads that libUv brings in so that the fundamentals becomes much more clear, anyways great video as ever :)
THNKAS A LOT i was havnig a hard time to get this idea but you have explained really simple, so Here you have a new student, thanks again and have a great day...and if your a reading this and your not the teacher , have a great day to smile, and remember you are important to.
For me the most tricky part is that you never really know when the function you call is going to be asynchronous or synchronous. For example if you read data from a file and then process it, for small files it will be synchronous and for the files with let's say 300k lines it will most likely be asynchronous (it also depends on what you do with these lines). It's obvious that all HTTP requests are asynchronous so this is quite easy to handle or predictable at least.
Something to add there is that. This is the event loop explained from the NodeJS side. If you take a look at the event loop in the browser side. It's much mure complex due to UI taks, Render Tasks, Dom Tasks, Net tasks.
Hi, 5:15 Eventloop use to take the event from queue and pushes into the callstack only when the callstack is empty. Means, eventloop do not take the event from the queue when there is an event(atleast 1) in the callstack. Am I right? What if there are multiple events waiting in event queue. Do the eventloop dequeues all the events one by one from eventqueue when the call stack is empty or it will dequeue only one event?
nice video but the title is a bit misleading, this is actually the node.js event loop as you say at the end of the video, not the javascript event loop as the title says.. JS natively does not use libuv, instead it uses the browser's built-in Web APIs to handle asynchronous tasks
Awesome! I have few questions 1. few days ago i was reading a medium article in which they use the term callback queue but here you mentioned event queue. 2 they called it Node APIs and you mentioned Libuv APIs. 3. They also did mention what's called MicroTask Queue, but here it was missing. 4. Does Event Loop handles only Async operations? 5. How does Event Loop handles setTimeout functions?
So I believe "callback queue" would be the same as the "event queue". I would assume Node APIs are also referring to the Libuv APis as well. I have never heard of the MicroTask Queue, so I'm not sure where that fits in. For the event loop, yes, it is only looking for async operations that have finished running. setTimeout takes a callback function. So, when setTimeout is called, it sends it off to the underlying APIs to be handled. When the timeout is done, it then throws the event/callback onto the Event Queue. The Event Loop will find the event on the queue and pass it back to JavaScript call stack. hope that helps!
Same doubt as yours, I just watched a different video where the event loop components are mentioned as follows: Call stack, event loop, micro tasks queue, macro tasks queue and scheduled tasks queue.
@@ivansandoval3757 You have probably watched the explanation of the browser event loop, whereas here it's the nodejs event loop They work in a different way. Not to mention the fact that browsers don't have the Libuv API
when synchronous code and a callback are both triggered at the same time, the synchronous code takes precedence over the callback function in the call stack. This means that the synchronous code will be executed first, and then the callback function will be added to the call stack and executed once the synchronous code has finished running.
so if we have async/await, it will put the asynchronous to libuv, then event queue, and stack it to the call stack along with the other synchronous tasks?
Thanks for the video! And yes, I have a question. So we know that every async procedure will go to the event queue. And it will only passed to the call stack if this is empty. So... 1. What about if we have a large large project, with many sync procedures, the event loop will wait until ALL of them finish before pass it to the call stack and give the result? 2. How it work then the "await", if we know that we need to clear the call stack before pass the async functionality. How it work when we need to have some data before proceed with the other instructions? For example data mutation 1, data mutation 2, data mutation 3, await for something() data mutation 4 How it works when we need to have the "something" before go to the data mutation 4 Thank you!
Understanding the LIFO/FIFO nature of the call stack vs the event stack is really cool, thank you.
So glad that was helpful :)
This is true but i think its important to not call event queue "stack" when the real data structure its a Queue. When you think about stacks and queues from real life everything makes sense
you mean event queue, not stack. Call Stack -- is stack, event queue - is queue.
Finally, after looking for n^1000 videos, forums... I found a person who can explain these terms in real simple and understandable way 😭really appreciate your work man.
Really? It was a very lame explanation. He skipped many essential parts while dragging on single things.
I loved it, thank you. It would be so great if you make a series like this , explaining advanced concepts under 5 minutes.
I've been developing in JavaScript for over 20 years now. But when I was interviewed recently for a new job, and asked about JavaScript event loop, I could not remember it for the life of me. This is mainly academical knowledge, not something that you need as an experienced developer. People who do interview are often dumb, and do not understand that.
...this video explains it poorly actually.
and you do need to know it.. you're wrong. not knowing event loop and execution context and enviorement and the phases.. is how people fck themsealves with accidental closures and other stuff...
most important part to know about event loop is about task queue and microtask queue, how microtask queue has priority,
and that web apis.. some of them are callback based, some of them are promise based ..
even setTimeout 1000ms for example.. is not 100% guaranteed,that it actually is 1000ms , that's not execution to time.. that's execution to enqueue of microtask queue.
one of the clearest explanation of event loop, thanks James
Yayyy!!
This is the best video that describes Event loop. Thank you so much for your work James!
Wow, thank you!!
Expected a 5 minute video but I got 2 whole extra minutes of James for free! What a deal
Always here to please!
Amazing video. Whenever I forget how it works I just jump over here and everything is clear again. Thank you mate!
Recently came across your channel and I’ve been learning so much. Thank you for all the work you put in on these!
Brilliant explanation with a clear design flow. Thanks, James!
As someone who is new to coding that explanation made the overall process really clarified things for me. Cheers
really well explained, thank you!!
i am really thankful for this video just before my interview, , feel having clear idea about what happen behind the scenes with node.js, please more advanced topics like this with such great explanantion
Wow, that's so cool to hear. Hope it went well!
Omg, thank you for this explanation. This was so straightforward and easy to understand.
really impressive thanks man
Glad you enjoyed it!
Always come here for a quick refresher before I have to explain it to anyone :) That article is excellent in itself too! great content!
Thanks for watching!
I watched a tens of videos to understand this. But this video very clear.
Broo you nailed it thank you and thanks to andrew for this informative explanation
Perfect explanation, thank you!
Awesome. It was Crisp, Precise, Easy to understand and To the Point.
Finally ! Amazing explanation Sir !
I like this overexplanation. Please do more. I am even watching tiktok videos that loop short coding lessons and they’re sinking in more.
Excellent explanation. This is exactly what I was looking for.
Thank you for that content. Keep going
Really nice and simple way of explaining complex concepts. Great video
That was amazing explaining, thank you so much
thank you for explaining this!
Super bro ... u explained a complex theory so simply with a beautiful animation.
Awesome explanation, much appreciated. Thanks :)
Amazing explanation. Thank you!
Hi , i was trying to wrap my head around the event loop, one suggestion for the video , a brief about v8 + libUv must have been wonderful specially mentioning about the 4 extra threads that libUv brings in so that the fundamentals becomes much more clear, anyways great video as ever :)
Great explanation here James!!!
This is amazing explanation !!! thank you!
Great and short tutorial! Highly recommended
Thanks for this!!!
Best video on node js event loop in 5 minutes
AYYYYY!!
Awsome sir now I understand watching many videos this is very simple to understand.
fantastic video, thanks!
great explanation!
Perfectly explained. Thank you
Very good explanation. Thanks
So glad it was helpful!
Great Explanation, Thanks a lot
Glad it helped!
Thanks Mr. Quick. This was neat magnificently explained
Thank you! Very concise and simple explanation of not an easy concept! 💛
Very clear explanation... great video!
Great video, keep going James! :)
I'm here with no background knowledge on JavaScript. I need to know this for an assignment and I find the video insanely easy to understand
Awesome tips!
Thank you! Glad it was helpful!
this explanation was amazing
Brilliant. I think I finally understand.
SUBBED!
awesome...thank you so much.
Amazing explanation!!
So glad you found it helpful!
Great content games🎉. Can you please share which software you used for visualisation?
Now I got it, thank you. That is a really great explanation James! You've got a new sub
Yayyyyy!!! Glad it helped!
THNKAS A LOT i was havnig a hard time to get this idea but you have explained really simple, so Here you have a new student, thanks again and have a great day...and if your a reading this and your not the teacher , have a great day to smile, and remember you are important to.
really well explained.
Thanks 🙌🏼
Woa truly appreciate it
Clearly understand ❤ followed
Great video, thank you!
very good explanation
For me the most tricky part is that you never really know when the function you call is going to be asynchronous or synchronous. For example if you read data from a file and then process it, for small files it will be synchronous and for the files with let's say 300k lines it will most likely be asynchronous (it also depends on what you do with these lines). It's obvious that all HTTP requests are asynchronous so this is quite easy to handle or predictable at least.
Well, I think you can tell something is asynchronous based on two things:
1. it returns a promise
or
2. if takes a callback function as a parameter
Amazing explanation, it was very clear! Thanks :)
Best explanation ever
Yes! So glad to help!
Wow, really, really understandable!!!
Thank you very much. It was explained very well and I finally understood what an JS Even Loop is. You did a great job in explaining it!
So glad to hear that!
wow great video , it simple thanks for the virtual presentation
note : libuv is written primarily in c ,
great explanation king
Thanks!
Thank you 👍👌
Something to add there is that. This is the event loop explained from the NodeJS side. If you take a look at the event loop in the browser side. It's much mure complex due to UI taks, Render Tasks, Dom Tasks, Net tasks.
I’m not sure that’s true? How is it different? It still uses the same offloading mechanism for async work right?
Hi, 5:15 Eventloop use to take the event from queue and pushes into the callstack only when the callstack is empty. Means, eventloop do not take the event from the queue when there is an event(atleast 1) in the callstack. Am I right?
What if there are multiple events waiting in event queue. Do the eventloop dequeues all the events one by one from eventqueue when the call stack is empty or it will dequeue only one event?
Thanks for the quick refresher, man! Plus correcting my pronunciation of "lib-you-vee" library ;)
Great explanation!
Thank you. Hope it helped!
Thank you so much...
Cleannnn thanks
thanks a lot man
thank you pls do not stop thank you
Getter and setter please and why using it
You're interested in why people use getters and setters?
Thanks!
Wow, I finally get it. Where does the heap come into this?
where I can find more videos on js concepts?
Clearly understand ❤️
Yay!! Glad to hear that!
U saved me man. Thank you.
Yay!!!
For 5 mins it is fine, but the micro task loop concept is missing
thanks bro
nice video but the title is a bit misleading, this is actually the node.js event loop as you say at the end of the video, not the javascript event loop as the title says.. JS natively does not use libuv, instead it uses the browser's built-in Web APIs to handle asynchronous tasks
Good correction
He says the event loop is "first in last out" is that out from the place it came it in or other end?
what does it mean when we say that event loop is blocked and how does that happen?
thanks
great explanation
Thank you! Did you already have a good idea of what the event loop is?
@@JamesQQuick nope not until today, learnt something new
@@krateskim4169 Ah so glad it helped!!
What about js workers? You can do multi threaded tasks with it.
Great video. One complaint, this is the node event loop which isn't exactly the same thing as JavaScript
Awesome! I have few questions 1. few days ago i was reading a medium article in which they use the term callback queue but here you mentioned event queue. 2 they called it Node APIs and you mentioned Libuv APIs. 3. They also did mention what's called MicroTask Queue, but here it was missing. 4. Does Event Loop handles only Async operations? 5. How does Event Loop handles setTimeout functions?
So I believe "callback queue" would be the same as the "event queue". I would assume Node APIs are also referring to the Libuv APis as well. I have never heard of the MicroTask Queue, so I'm not sure where that fits in. For the event loop, yes, it is only looking for async operations that have finished running.
setTimeout takes a callback function. So, when setTimeout is called, it sends it off to the underlying APIs to be handled. When the timeout is done, it then throws the event/callback onto the Event Queue. The Event Loop will find the event on the queue and pass it back to JavaScript call stack.
hope that helps!
Same doubt as yours, I just watched a different video where the event loop components are mentioned as follows: Call stack, event loop, micro tasks queue, macro tasks queue and scheduled tasks queue.
@@ivansandoval3757 You have probably watched the explanation of the browser event loop, whereas here it's the nodejs event loop
They work in a different way. Not to mention the fact that browsers don't have the Libuv API
Hi there, I'm watching this in April - if I sign up on the website you linked, can I still see the 24 JS and CSS challenges you did for Advent?
Yep!
so if there is an incoming synchronous code and a callback at the same given time, what is the precedence for the call stack?
when synchronous code and a callback are both triggered at the same time, the synchronous code takes precedence over the callback function in the call stack. This means that the synchronous code will be executed first, and then the callback function will be added to the call stack and executed once the synchronous code has finished running.
great video
so if we have async/await, it will put the asynchronous to libuv, then event queue, and stack it to the call stack along with the other synchronous tasks?
Thanks for the video! And yes, I have a question.
So we know that every async procedure will go to the event queue. And it will only passed to the call stack if this is empty.
So...
1. What about if we have a large large project, with many sync procedures, the event loop will wait until ALL of them finish before pass it to the call stack and give the result?
2. How it work then the "await", if we know that we need to clear the call stack before pass the async functionality. How it work when we need to have some data before proceed with the other instructions?
For example
data mutation 1,
data mutation 2,
data mutation 3,
await for something()
data mutation 4
How it works when we need to have the "something" before go to the data mutation 4
Thank you!
Wonderful Info Sir! please make a series on vue js
Glad you enjoyed it! I still haven’t really spent time with vue yet but I want to!
Okay this is Node platform with C++ wrapper. but what about browser where we dont have Node and still have async JS?