how to find what is currently in the callback queue in nodejs - javascript

I'm looking at some code that uses setInterval to call a function every 30 seconds, but it doesn't look like it's firing every 30 seconds, in fact it fires every 3 minutes roughly. I think it's because there are other functions enqueued and it takes a while to get to call this function. Please correct me if I'm wrong.
Is there any way to check what's there on the callback queue either visually or even something simple to dump every 1 sec to some log file?

You can use process._getActiveHandles() and process._getActiveRequests()
See this discussion in node.js mailing list.
update: there is a good package for this - https://github.com/mafintosh/why-is-node-running

You can use this to check that it is called e.g. every 30 seconds:
setInterval(function() { console.log(new Date());}, 30000);

Related

I need help creating a loop in dev console in firefox

I am trying to use the dev console to give mario a mushroom every 5 seconds (in the browser game super mario html5)
I can give mario mushrooms manually by typing marioShroons(mario) but I would like to have it on loop so I don't have to pause the game every time I want a mushroom. I have tried a while loop and set timeout but I can't figure it out. The only coding languages I familiar with are c++ and html.
**
while(data.time.amount > 0) {
killOtherCharacters()
}
setTimeout(function() {
killOtherCharacters()
}, 1000);
I expected these lines of code to not give me a mushroom, but to automatically kill enemies. But on the first try (the while loop) it froze the tab and I had to reload the page.
With the set timeout, it didn't make any obvious results, it killed all near characters once and then stopped.
You tried using setTimeout, and it only worked once. This is to be expected, because:
Window.setTimeout() sets a timer which executes a function or specified piece of code once the timer expires
From MDN
What you need to do is use setInterval:
The setInterval() method...repeatedly calls a function or executes a code snippet, with a fixed time delay between each call.
From MDN
So in your console, you should write this:
setInterval(killOtherCharacters, 1000);
(I removed the anonymous function because it wasn't needed - you only need an anonymous function if you're passing parameters or doing multiple things. You do need to remove the () for this though).
And if you want to stop the function from executing, assign a variable to the interval:
var killCharacters = setInterval(killOtherCharacters, 1000);
Then call clearInterval upon this variable to clear the interval (stop the loop):
clearInterval(killCharacters);
The reason your while loop froze the page is because Javascript can only do one thing at a time and you told it to always run your while function, blocking all other Javascript from running on your site.
setTimeout is only run once after a set time (see documentation), if you want to run something every x miliseconds it's better to use setInterval instead.
var intervalID = window.setInterval(killOtherCharacters(), 500); //run this every 500 ms
Use setInterval if you want killOtherCharacters() to be called repeatedly.
const interval = setInterval(function() {killOtherCharacters() },1000);
Then when you want the function to stop being called:
clearInterval(interval);

setInterval function using jquery is causing a "blink"

Personal project using jQuery.
I'm trying to create a function that runs on the hour for 5 seconds. I've done this by getting the current minutes and acting when they are at '00'. (Although for testing the minutes need to be manually changed to the next minute, unless you want to wait an hour to see it run again.)
The function acts on 2 objects, one to add/remove a class, the other to slideUp/Down.
It works, but after the initial running, the slideDown/Up jQuery causes a "blink" every 5 seconds for the rest of the current minute.
I've tried setting the setInterval for 5000, however that hasn't solved the issue. I'm at my wits end really.
While I am also using moment.js elsewhere. This function isn't using moment(). Primarily because I haven't been able to get functions working with moment() either.
Just head to the ....
jsFiddle example
Remember to set the =='00' to the next minute -- sure makes testing easier I really appreciate anyone waiting for this to run. I know it can be a pain to have to wait a minute to see the function at work.
If you watch the function run for 5 seconds, it will stop... but continue watching.. the slideDown() will repeat every 5 seconds until the minute is no longer XX.
How can I stop this repeat??
Thanks!
There're two place for fix.
1. miss usage for 'clearInterval'
clearInterval parameter is The ID of the timer returned by the setInterval() method.
reference this link, w3c definition for clearInterval.
var intervalId = setInterval(function() { alarm(); }, 5000);
...
clearInterval(intervalId );
2. secs >= "05" condition is wrong
change string "05" to int 5.
Believe it or not I sorted it a few moments after posting this.
My conditional was off, and I thought I tried everything. Guess not.
This works
if((mins == "29") && (secs <= '05')) {
$('#focus').slideDown(500);
$('.projcnt').addClass('jump');
} else {
$('#focus').slideUp(300);
$('.projcnt').removeClass('jump');
}
And the ...
working, updated fiddle

Is setTimeout safe for scheduling jobs over large spans of time?

I'm writing an application in Node.js that needs to schedule functions to be run at specific times. Hours or sometimes days in the future. Currently, I'm doing so with something similar to this:
const now = Date.now();
const later = getSomeFutureTimestamp();
setTimeout(function() {
// do something
}, later - now);
I'm wondering if setTimeout is the proper tool for this job or if there is a tool more suited for long intervals of time. One thing to note is I don't need great precision; if the job runs within a few minutes of the scheduled time, everything should still be fine.
setTimeout should be fine. It's only really delayed if there's blocking code running at the moment when it's meant to execute. So setTimeout is typically 20 milliseconds late. But since your margin is minutes, I don't think it'll be an issue.
However, I'd suggest storing the timestamp at which things should trigger, and just periodically check. That way you only have 1 timer running at any given time.
You also get to keep your timestamps as absolute timestamps - not as relative, "milliseconds in the future" values. That also lets you store them between server restarts, which you can't do as easily with relative times. With your code, the only record of a job being queued is that there's a timer running. If that timer disappears for any reason, you lose all record of a job having been scheduled.
Something like:
function checkForScheduledJobs() {
var now = Date.now(),
job;
// assuming here that the jobs array is sorted earliest to latest
while(jobs.length && jobs[0].timestamp < now) {
jobs.shift().callback();
}
setTimeout(checkForScheduledJobs, 60000); // check each minute
}
You just need to kick it off once. This could be done in an addScheduledJob function (which would also sort the jobs array after adding something to it, etc.)

Creating a Jquery update function?

How can I create an update function in javascript/jquery?
An update function is a function that is run at each step in the game, say 60 times a second for example. It is used a lot in game development.
How can I make something like this in jquery?
Probably you need to use setInterval function.
But I would recommend to use requestAnimationFrame instead as it was designed for developing browser games and can perform 60 calls per second as you need.
why jQuery? just call a function with a frequency of 1000/60 msecs, e.g.
setInterval(function() {
...
}, 1000/60)
SetInterval will be useful to you in this instance.
You can use it like this -
var timer = setInterval(callback,delay);
This code will execute a function named callback every delay miliseconds.
To stop the timer, you can use the clearInterval() method.
clearInterval(timer);
As I stated, the intervals are defined in milliseconds so in order for your callback to execute 60 times a second you would need to pass 16 or 17 milliseconds as the delay parameter.
That will partially depend on your rendering method.
If you will be rendering your "game" in (for instance) a <canvas> element, you might want to use requestAnimationFrame (a javascript native function)
For more information see This helpfull article

Is it possible to make an alarm in javascript?

Is it possible to ser a function to start in a given date and hour? How?
I thought about setTimeout, but what's the maximum time I can set?
--update
By the way, it's for a desktop application.
I agree with JCOC611 - if you can make sure that your application does not close, then just get a Date object of when your alarm should go off and do something like this:
window.setTimeout(function() { soundAlarm() },
alarmDate.getTime() - new Date().getTime());
I see no reason for this not to work, but a lot of people exalt a timer based solution where you have a short lived timer that ticks until the set time. It has the advantage that the timer function can also update a clock or a countdown. I like to write this pattern like this:
(function(targetDate) {
if (targetDate.getTime() <= new Date().getTime()) {
soundAlarm();
return;
}
// maybe update a time display here?
window.setTimeout(arguments.callee,1000,targetDate); // tick every second
})(alarmDate);
This is basically a function that when called with a target date to sound an alarm on, re-calls itself every second to check if the time has not elapsed yet.
setTimeout(functionToCall,delayToWait)
As stated in Why does setTimeout() "break" for large millisecond delay values?, it uses a 32 bit int to store the delay so the max value allowed would be 2147483647
Does setTimeout() have a maximum?
http://www.highdots.com/forums/javascript/settimeout-ecma-166425.html
It may surprise you that setTimeout is
not covered by an ECMA standard, nor
by a W3C standard. There are some
holes in the web standards. This is
one of them. I'm looking to the WHAT
Working Group to fix this. See
http://www.whatwg.org/specs/web-apps/current-work/
There doesn't seem to be a problem in
setting the timeout value to something
that is vastly greater than the MTBF
of the browser. All that means is that
the timeout may never fire.
http://javascript.crockford.com/
-Douglas Crockford
As others have mentioned, this isn't the way to handle the situation. Use setTimeout to check a date object and then fire the event at the appropriate time. Some code to play with is linked below.
http://www.w3schools.com/js/tryit.asp?filename=tryjs_timing_clock
You should not relay on setTimeout for the actual alarm trigger but for a periodic function tracking the alarm. Use setTimeout to check the stored time for your alarm say every minute. Store that time in DB, file or server.
Is there any server component to this at all? You could use setInterval to call something serverside on a regular basis via ajax, then pull back a date object and once it's finally in the past you could trigger your "alarm"

Categories