DEV Community


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

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));
Enter fullscreen mode Exit fullscreen mode 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

Thread Thread
techygeeky profile image
Kapil Raghuwanshi🖥 Author

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