Variable declaration when destructuring an array in JavaScript

It is not necessary to declare variables when destructuring. They can be declared in advance and then when assigning it will not be necessary to write the command let:

let arr = [2025, 12, 31];
let year;
let month;
let day;

[year, month, day] = arr;

There are, however, some nuances. Look at the following code:

let arr = [2025, 12, 31];
let year;

let [year, month, day] = arr;

As you can see, the variable year has been declared in advance, but the variables month and day have not. So the author of the code decided to write let before the destructuring assignment.

This, however, will lead to an error, since it is impossible to declare the same variable twice through let (it turns out that year is declared twice).