What is this code doing in the loop?

Question

typescript

for (const [node, linkedLayers] of groups) {}

groups is Map()

Do I understand correctly that the key flies to the node variable, and the values ​​to linkedLayers . But why in square brackets instead of {}?

Answer 1

https://developer.mozilla.org/en/docs/Web/JavaScri...
read the section "Map iteration with for..of"
Why so? Well, because the built-in Map iterator returns an array of [key, value], those are the rules of the language. We can say that this is a shorthand for map.entries().
It also works in the opposite direction, such as

const first = new Map([
  [1, 'one'],
  [2, 'two'],
  [3, 'three'],
]);

Answer 2

Array destructuring

Answer 3

This is a group assignment

c = [1,2];
[a,b] = c;

a=1 and b=2