default value in destructuring code example

Example 1: javascript function destructuring

function f() {
  return [1, 2];
}

let a, b; 
[a, b] = f(); 
console.log(a); // 1
console.log(b); // 2

Example 2: mdn destructuring

let a, b;

[a, b] = [1, 2];
console.log(a); // 1
console.log(b); // 2