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Discussion on: Top 20 JavaScript tips and tricks to increase your Speed and Efficiency

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Replies for: Enjoy: const matrix = (x, y = x, fillValue = 0) => Array.from({ length: y }, () => Array(x).fill(fillValue)); Enter fullscreen mode...

 
techygeeky profile image
Kapil Raghuwanshi🖥 •

How about these two?

const arr = Array.from(Array(4).fill('O'), () => new Array(4).fill('O'));
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const arr = [...Array(8)].map(() => Array(8).fill("0"))
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snigo profile image
Igor Snitkin • • Edited

If we talk about efficiency, then we first need to figure out .map or .from:

  • map: maps over elements returning new array 👎
  • from: mapFn maps over elements in place 👍

So from, which leaves us with the question what we're going to create our array from, right? So if we compare:

// Array from array
Array.from(Array(3), () => Array(3).fill(0));

// Array from object
Array.from({ length: 3 }, () => Array(3).fill(0));
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...it will boil down to the question what's more efficient to create Array(3) or { length: 3 }, and given arrays in JS are just objects it really comes to the number of properties we need to create for the object. How many properties does Array(3) have? (hint: 4) How many properties does { length: 3 } have? (hint: 1)

I hope this will clear things a bit

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techygeeky profile image
Kapil Raghuwanshi🖥 •

Awesome and detailed explanation @snigo . ✌🏻
I have created GitHub Repo, feel free to contribute to that.
Thanks!🤗