
# `setInterval` in Javascript doesn't run as expected

Early this year, we had to implement a countdown timer for a survey. When the timer is up, participants will not be able to continue answering it. We used the `setInterval` and implemented a function that minus the time by the second.

When our client tested it, she felt like the timer got paused when her browser idled or whenever she switched to another window. It seems that `setInterval` is not triggered, and it happens quickly after a few minutes of starting the survey.

We took it back to check the issue on our environment. At first, we couldn't replicate the bug, but we thought it's because our machine had more power, therfore it may be running fine. But as we kept it running for some duration (at about the hour mark), the issue started to appear. Instead of calling every second, our method is called every minute!

![lalt](/setInterval.png)

You could argue that this is only aesthetic as no one can see the clock ticking down if the browser is idled or switches tab. But we implemented other checks on each second such as kicking out from the survey if the expected time is up. There is also an implementation where it will auto pause the survey if the expected reponse from the client to the server is delayed. This is an indication if client loses the internet connection while in the survey.

A quick Google search led us to this [article](https://developer.mozilla.org/en-US/docs/Web/JavaScript/EventLoop). Since Javascript is a single-threaded language, any callback methods is queued in an event loop. Which includes the `setInterval` and `setTimeout` methods. Any queues in an event loop, will not be guaranteed to be executed based on the time to execute, as that is only a minimum guaranteed time. 

As an example, below is a code that I slightly modified from the article I pasted earlier. 

```
(function() {

  console.log('this is the start');

  setTimeout(function cb() {
    console.log('Callback 1: this is a msg from call back');
  }); // has a default time value of 0

  console.log('message 2');

  setTimeout(function cb1() {
    console.log('Callback 2: this is a msg from call back');
  }, 0);

  console.log('message 3');

})();
```

We would have thought that Callback 1 is called first as the setTimeout callback time defaults to 0, followed by message 2, and so on. But the actual output will be as follows:

```
// "this is the start"
// "message 2"
// "message 3"
// "Callback 1: this is a msg from call back"
// "Callback 2: this is a msg from call back"
```

There are various ways to mitigate this. One way is to use `Window.requestAnimationFrame()`. It will call a specific method to update the frame and is separated from the main event loop. However, if the current window or tab is idle, it will be suppressed to save battery and improve performance. ([article](https://developer.mozilla.org/en-US/docs/Web/API/window/requestAnimationFrame))

> `requestAnimationFrame()` calls are paused in most browsers when running in background tabs or hidden `<iframe>`s in order to improve performance and battery life.   

We end up with using `setTimeout` still. It is not the perfect solution, but it still keeps the timer running as if it is running down by the second. We checked the drift value, the time difference between the expected call time versus the actual time the method is called. When the drift exceeds a certain threshold, we set the next `setTimeout` a little quicker, so we maintain the method calls does not drift further away.

Here is an [example](https://github.com/zaidrashid/js-playground/blob/main/timer.js) of how we implemented it. The code is a standard timer tick instead of a countdown, but the concept is similar.

I still think that we could improve it, such as implementing `requestAnimationFrame()` for the UI while implementing the lock and extension of time at the backend. I also saw other examples on the internet that handles the drift values more aggressive, but this implementation suffice our needs so far. Let me know what you think, and feel free to show me a better way of handling it. 

setInterval in Javascript doesn't run as expected


# JS: Regex replacement with matching groups

When doing a `.replace()` with regex, you might want to replace some group of strings, but leave some of it. Of course, you can use group matching. To do that, simply use `$n` where n is a positive number from `1-100` representing the matched group number. Example:

```jsx
fileName = 2022-07-15-some-title.md;
fileName.replace(/(\d{4}-\d{2}-\d{2}-)(.*)(\.md$)/, '$2');

// the result of the replace will be...
// "some-title"
```

If we have a `fileName = 2022-07-15-some-title.md` then the code above will only replace with the second (`$2`) matching group. The result will be `some-title`

JS: Regex replacement with matching groups


# On losing weight; How I lost weight from 81kg to 67kg.

## Disclaimer: 
> Do not take this as any form of medical advice. Please consult your doctor first.
## TLDR:
>I tried intermittent fasting because of laziness and realized that I am OK with eating less. Felt better and had more energy. I found out that I like running and was able to find time to do it. It's already a one-year journey and still ongoing, but the key is finding what suits you best and just being consistent.

One day in the early days of December 2020, I woke up feeling groggy and tired. I was moody and felt out of breath. I made breakfast, which at that time was an important thing to do first, or otherwise, my temper would be out of control. Someone I knew termed it as "hangry" (angry + hungry). Overall, I wasn't feeling good, but it wasn't that sick "feeling not good" but rather more like being mentally exhausted, tired, and lazy, and having it almost every day. 

When doing video calls with my parents back home in Malaysia, they commented that I have been putting on weight. I didn't know how heavy I was then and guessed it should be around 70kg. That should put me in a slightly overweight category according to the BMI. (I'm Asian and pretty short). It's not going to be that bad, so I thought.

So I bought a scale from Amazon, and when it arrived, I weight 81kg! That's almost in the category of obese (29.3). I should do something.

At first thought, I should start exercising but quickly dismissed it. I'm not an active person, and I don't have time to do it, nor do I want to find time for it. So should I be controlling my diet then? However, I don't want to restrict myself to certain foods, and even if I do, I'm not good at managing my intake. I was known as the dustbin in my family because I would finish all the foods that my family members couldn't. 

So the only possible way to start and not put on any high burden on this journey is to fast. As a practicing Muslim and being used to fasting during the month of Ramadhan, this should be easy. I've also come across articles and videos of health practitioners recommending to go on fasting once in a while, so I thought this should be doable. The idea is to go for 16 hours of fasting, don't eat or drink except for non-calories food, which is only water, coffee, or tea (plain without milk or sugar), and the recommended time is from 9 pm to 1 pm the next day. Between 1 pm to 9 pm, you'll eat normally. I decided to start with this, as:

1) I don't have to do any exercise 
2) Give up breakfast which saves time and money, 
3) Still be able to drink coffee as I am a black coffee drinker and,
4) I could eat as much as I want between 1 pm to 9 pm.

But honestly, it wasn't easy, especially the first three weeks. I kept looking at my watch, waiting for it to strike at 1 o'clock. I'll stuff all I can between the non-fasting period, and I would overindulge as much as I can when it nears 9 pm. During the day, weird rumbling sounds will come from my stomach that my colleague sitting in front could hear them. Embarrassingly, my stomach will let out a lot of air (yes, fart) and feel like it is adjusting somewhere inside.

But soon, I started to feel all right. And I got used to it. By the 4th week, I begin not to care if I break my fast a few minutes late. I can't eat that many because I will quickly feel full (by eating less). And I'll finish my dinner at around 8 pm, and stop eating by then instead of 9 pm. I'm eating less but was perfectly fine with it.

In just a month, I weigh around 76kg, less than 4-5 kg from the start. But by September, I was weighing 74kg. Despite only doing intermittent fasting (I did miss a few days, but it is rare and less compared to most of the days), the total loss so far is around 5-6kg within nine months, which is not that bad. But it was not a big, impactful kind of a result in any way. The thing is, I started to weigh around 74kg in February 2021, and by September, that is still my average weight. It seems that I am reaching a plateau.

However, there are a few things that I noticed. I do feel much better. I sense that I have more energy and feel fine throughout the day. I sleep consistently, and my consumption of food changes. For example, I will go for well-balanced food during lunch that makes me full. Therefore I don't feel the urge to go snacking in between. For some reason, I eat less sugary things too and probably would go for fruits, for example. It's not that I don't eat at all, but I realized that consumption of unhealthy, non-balanced food decreases.

Now that I am realizing my weight is plateauing, I began to think about exercising again. Yes, I am no longer opposed to the idea of exercising, and that is because of having the feeling of being well-rested and having a bit more energy. After all, everyone agrees exercising is good. But I don't want to drag myself outside or subscribe to a gym. So I started to follow some indoor workouts from Youtube or download an app to my phone. I hated it. It's painful and felt meaningless because the easy levels would be boring, and the medium or hard levels felt too much for me. I don't know where to start or to focus on. Should I go for legs or upper body? And I don't like spending time choosing which exercise or course to follow. It all seems the same to me. Probably this is not for me after all. Maybe not yet.

But I still haven't given up the thought yet. So I looked around and decided that I could try running. I have to admit that I live in an area that provides long routes to run. We've got parks, farm roads, forests, and almost all path is connected with a bicycle or walk path, which gives you safety while running. So I bought a running shoe and hit the road. It was painful too, but at least I'm seeing a target like the next house or a junction and trying to run it. Even if I am halfway through and decide to give up, I can't simply stop and sit on a couch. I still have to walk back home. At first, I couldn't run for 2 km, so I researched what I did wrong. I realized that there are techniques, and proper ways to start running. For example, starting slowly and maintaining your heart rate so you could run longer. I just kept running again for the next day or week, and surprisingly it felt better, and most importantly, I started to enjoy it. 

That feeling of your first 5 km, and then hitting 10 km is so much rewarding. Now I can run 10 km consistently weekly, and slowly try to increase towards 15km. My goal would try an unofficial half marathon by this summer.

Anyway, going back to my weight currently in January 2022, I am at 67kg. I am still doing my intermittent fasting, except when I go for long runs, which I will eat breakfast after finishing a run. It hits me, you just need to find what suits you best and be consistent. 

I know people out there would try to reduce their weight. Such irony is that this usually comes up every new year. "Next year, I will go on a diet, I will eat only protein and will be in shape again." It sounds a bit too extreme for me. Usually, this will not work out. I know because I am one of those many years ago.

When I thought about "doing something", I knew that switching to a hard diet overnight, or starting with exercising while I know I am not that kind of person, will put my path to failure. So, I start with the least I can do and try to be consistent. After one year of intermittent fasting and exercising (just started a few months), it seems to be working for me, and I plan to continue with it.

For you reading this, try out what's best for you, do it, and be consistent. 

Good luck!


















 



On losing weight; How I lost weight from 81kg to 67kg.


# Updated Site

It's been long overdue since I've updated my website. The last update was in 2015 when I first learned AngularJS and we all can agree that it is ending its long term support (LTS) at the end of this [year](https://blog.angular.io/stable-angularjs-and-long-term-support-7e077635ee9c)

This site will serve as my occasional writings of thoughts and opinions. I  will be writing in English or [Malay](https://en.wikipedia.org/wiki/Malay_language) and will be on various topics.

Cheers!