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

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));

...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