Event loop refers to an infinite cycle of actions which is used for processing data based on callbacks and messages.
An event loop watches for I/O and timer state changes. It queues functions while waiting for unavailable resources, then dispatches them when resources are available.
From what I see, if an event in Node take a "long time" to be dispatched, Node creates some kind of "queue of events", and they are triggered as soon as possible, one by one.
How long can this queue be?
I've done lots of development in C#/.Net, and the asynchronous story has always been there from day one (admittedly the API's have changed significantly over the years from begin/end to events, to Task with async/await). For the last year or so…
The following figure is taken from Chapter 3 of the book Secrets of the JavaScript Ninja by Jon Resig. Here the author is explaining the browser event loop.
The book has to say this :
It’s important to note that the browser mechanism that puts the…
I first tried a general description of the problem, then some more detail why the usual approaches don't work. If you would like to read these abstracted explanations go on. In the end I explain the greater problem and the specific application, so…
In the following code:
setTimeout(() => console.log("hello"), 0);
Promise.resolve('Success!')
.then(console.log)
What should happen in my understanding:
setTimeout is called => print hello directly added to callback queue as time is…
Requirement is concurrent request 1000 per second and IO operation such as database queries on each request. As nodejs works on event loop and it will assign the IO operation to thread pool, but thread pool default size is 4, so at same time maximum…
So I been reading a tutorial about Javascript promises these days.
here is an example from it used to explain the macrotask queue(i.e. the event loop) and the microtask queue.
let promise = Promise.reject(new Error("Promise…
I was going through node docs for event loop and I got very confused.
It says -
timers: this phase executes callbacks scheduled by setTimeout() and
setInterval().
I/O callbacks: executes almost all callbacks with the exception of close callbacks,…
I want use the Python 3 asyncio module to create a server application.
I use a main event loop to listen to the network, and when new data is received it will do some compute and send the result to the client. Does 'do some compute' need a new event…
I've been reading some NodeJs articles in order to understand its async nature during which I found this and really liked it Node.js, Doctor’s Offices and Fast Food Restaurants – Understanding Event-driven Programming
There is a thing called…
First of all, I am starter trying to understand what is Node.Js. I have two questions.
First Question
From the article of Felix, it said "there can only be one callback firing at the same time. Until that callback has finished executing, all other…
I wonder how the event-loop works in javascript,
I am using node.js but I guess that the same question apply to browsers.
I have some async call (let's say setTimeout or $.ajax or fs.readFile)
and after a while the event-loop executes the…
It's better to write code that doesn't rely on the timing of immediate callbacks (like microtasks vs macrotasks), but let's put that aside for the moment.
setTimeout queues a macrotask, which, at a minimum, waits to start until all microtasks (and…
The general perception is that JavaScript is intrinsically single-threaded but it can run asynchronously. I wonder how a single-threaded model like this handles AJAX requests that are non-blocking?
Lets say a non-blocking AJAX request is fired in a…
Is there any way by which one can apply priority to Node.js task's in a event loop.
I want to assign priority to task which are present in a event loop of nodejs.
Suppose in a event loop there are 5 jobs A,B,C,D,E which having same priority and then…
