DEV Community: Jarett Lee

Which would you use? Regarding _.chunk

Jarett Lee — Fri, 15 Nov 2019 05:21:48 +0000

I was looking through the You Don't Need Lodash repo and I decided to take a crack at making my own _.chunk function.

// === sample 1 ===
// I think this is clear and avoids mutable data. The basic idea is:
//   1. make a new sub array when you need a new sub array
//   2. keep the old stuff and add the new thing to the end
const chunk = (input, size) => {
  return input.reduce((arr, item, idx) => {
    return idx % size === 0
      ? [...arr, [item]]
      : [...arr.slice(0, -1), [...arr.slice(-1)[0], item]];
  }, []);
};

// === sample 1.2 ===
// I think this is a slightly clearer way to state that you need a new sub array
const chunk = (input, size) => {
  return input.reduce((arr, item, idx) => {
    return arr.length === 0 || arr.slice(-1)[0].length === size
      ? [...arr, [item]]
      : [...arr.slice(0, -1), [...arr.slice(-1)[0], item]];
  }, []);
};

// === sample 1.3 ===
// Naming the sub array might be most clear.
const chunk = (input, size) => {
  return input.reduce((arr, item) => {
    const subArr = arr.slice(-1)[0];
    return arr.length === 0 || subArr.length === size
      ? [...arr, [item]]
      : [...arr.slice(0, -1), [...subArr, item]];
  }, []);
};


// === sample 2 ===
// I think this is also clear, but uses mutable data. The basic idea is:
//   1. fill a sub array
//   2. when a sub array is full, create a new sub array and append it to the
//      main array
const chunk = (input, size) => {
  return input.reduce(({arr, subArr}, item) => {
    if (subArr === undefined || subArr.length === size) {
      subArr = [item];
      arr.push(subArr);
    } else {
      subArr.push(item);
    }

    return {arr, subArr};
  }, {arr: [], subArr: undefined}).arr;
};

// === sample 2.1 ===
// Here's the same function as sample 2 using a loop
const chunk = (input, size) => {
  const arr = [];
  let subArr = [];
  for (item of input) {
    if (arr.length === 0 || subArr.length === size) {
      subArr = [item];
      arr.push(subArr);
    } else {
      subArr.push(item);
    }
  }
  return arr;
};

// === sample 3 ===
// Here's a mathy version. I'm not a fan since it's harder to explain this in a
// simple way.
function chunk(input, size) {
  var arr = [];
  for (var idx = 0; idx < input.length; idx++) {
    var item = input[idx];
    var newIdx = Math.floor(idx / size);
    var newSubIdx = idx - newIdx * size;

    if (idx % size === 0) arr[newIdx] = [];
       arr[newIdx][newSubIdx] = item;
  }
  return arr;
}

I think my favorite is sample 1.3 since it avoids mutable data and is clear to me. Which function would you use? Would you make your own?

Edit: I had a mistake in my initial code when I didn't handle when arr.length === 0 in this code arr.length === 0 || subArr.length === size. This makes the samples slightly less nice, but still relatively clear in my opinion.

What does the 20-20-20 rule really do?

Jarett Lee — Thu, 17 Oct 2019 02:37:17 +0000

I was recently browsing the most popular articles on dev.to and I came across The Definitive Guide To Protecting Your Eyes For Developers👀. It was an interesting read with a bunch of eye tips, but I finished wondering if I should be taking health tips from a random article online without any sources. So, I did some digging and I found that the article is somewhat misleading.

First, "staring at a screen for long hours" will not cause nearsightedness or farsightedness. The light from a screen may feel different, but it's pretty much the same as light from the sun. It's only really different in one way, light from laptops is a lot weaker than sunlight (1). The screen light alone does nothing; it's how we interact with screens.

When on a screen, we often sit still, forget to blink, and keep our eyeballs still. These things can cause blurred vision, headaches, and pain in the neck and shoulders. If you want to google it, these causes and symptoms are collectively called digital eye strain. I consider this term somewhat strange since the symptoms affect more than your eyes and can be caused by a variety of reasons, but I digress. These symptoms are short-term (2) and are actually what the 20-20-20 rule ("Every 20 minutes, look at something 20 feet away for 20 seconds.") is trying to solve. However, if you're like me and don't have trouble with eye strain, you don't have to worry about the 20-20-20 rule at all.

As for the rest of the tips, I would appreciate if people could help me check them, as well. In fact, check this article as well. The original author, Sarthak, and I both agree our eyes are important.

As a note, I have nothing against the original author, Sarthak Sharma, for writing the original article. I just want to extend the conversation that he started.

Sources

(1) Primary source https://www.nature.com/articles/eye2015261.pdf
(2) Secondary source https://www.news-medical.net/health/Does-looking-at-a-computer-damage-your-eyes.aspx

Gut feeling guide

Here's a gut feeling guide without any sources for myself.

If you have eye strain the 20-20-20 rule works and apps can help remind you to look away.
Bouncing a ball against a wall would gets your eyes moving, so I assume it also helps with eye strain.
I have no idea if water massages help, but they sure do feel good.
f.lux is actually concerned about how blue light from screens is similar to the sun, so it messes with your sleep schedule, not with your eyes. Sarthak mentions this in his article. I think I read somewhere that this is backed by science, but I don't have the sources right now.
I assume diet is important for eyes, but diet science tough to validate, so I won't get into that.
I don't know about younger folks, but older folks (55+) should get eye check-ups! You might identify Glaucoma, a condition that can permanently harm your eyes.
Glasses with the wrong prescriptions can cause eye strain, but I don't believe it causes long-term damage.

You might have noticed that the only thing that might actually help avoid glasses is diet and identifying eye diseases. I found it disheartening to find this, since neither feel very effective, but sometimes that's the reality of the situation. The only other things you can do to protect your long-term eyesight are apparently to exercise and avoid smoking.

What code have you read recently?

Jarett Lee — Tue, 17 Sep 2019 21:09:57 +0000

I recently read Peter Seibel's Code is Not Literature where he observers that in order to understand code, we more often have to decode and play with the code rather than simply reading it. This made me wonder if others have run into code so clear that you can understand it just by reading it?