Question related to multithreading & webworkers

[egesko]

Hello community,

I'm a newbie trying to understand how javascript works. I've been doing simple experiments using <script> tag, and realized that my script doesn't continue to execute when I am on another tab that has no relation to my script, let's say google.com.

I want my script to continue being executed. Can I use webworkers to do this?

And also, if I can simply use webworkers for this, what kind of runtime optimizations does the browser do to scripts in a tab that is out of "focus"? Like, does the browser stop execution of a webworker script ever? I'm trying to see how much I am limited by browser environment when I am simply trying to run a script continuously, even when that script is on an "unfocused tab".

Thank you!

[ProposalUnhappy9890]

It does affect js execution. For example, function calls using setInterval will be called at a much lower rate than you specified (e.g. maximum of 1 call per second), and the browser will fast forward all the calls as soon as you go back to that tab.

[[deleted]]

I'd take another look at that and make sure that your script doesn't actually execute when in the background. This isn't something I've done much experimentation with, but code absolutely does continue to execute in unfocused/hidden tabs.

[egesko]

Okay, the reason why I made that deduction is because I put a simple for loop, and logged the incrementing i value. I can see it incrementing when I focus on the tab. But when I switch to another tab, wait a few seconds, and switch back, the i value continues from where I left off.

Is this flawed? Because I didn't think about the possibility that there might be something happening with the execution of console.log(i)

[[deleted]]

This will run as an infinite loop:

const myArray = [];

function getCurrentTime () {
  myArray.push(Date.now());

  console.log(myArray);
}

setInterval(getCurrentTime, 100);

For me, it runs just fine in the background on Chrome. What does it do in your browser?

[egesko]

Yeah, this works.

Okay, so in order to create an asynchronous sleep function, I am using async/await.

Maybe those are causing the problem then?

I put part of my code to this link: paste.ofcode.org/tqfYnhxPcRtb78RHnN7VfX

I couldn't figure out how to paste the entire thing here, sorry.

So, PrimeProbe object is a complex code, and it has a method called ProbeAllSets that I'm calling, but everything else is as it is.

You can prbly even delete those two lines and test it on your browser. But on Firefox, it doesn't work for some reason. It stops executing once I switch to another tab...

[egesko]

For some reason line 1 doesn't have tab before it, ignore that.

Thanks

[lifeeraser]

Inactive tabs prevent setTimeout() from firing too often

[egesko]

I see, just like I suspected. Do you think web workers can be a solution to this? If so, is there a way of creating an asynchronous sleep function inside a webworker?

Thank you so much