let a = 0;
function sum() {
function increaseSum() {
// the value of a is increased by 1
return a = a + 1;
}
return increaseSum;
}
const x = sum();
console.log(x()); // 1
console.log(x()); // 2
console.log(x()); // 3
a = a + 1;
console.log(a); // 4