overloading Javascript functions, unlimited sum

sum.js

function unlimitedAdd(...nums) {
  const func = unlimitedAdd;
  func.sum = nums.reduce((total, current) => total + current, 0) + (func.sum || 0);
  func.done = function() {
    return func.sum;
  }
  
  return func;
}


let a = unlimitedAdd(1,2,3);
console.log(a.done())
a = a(4,5);
console.log(a.done())
a = a(6,7,8);
console.log(a.done())
a = a(14);
console.log(a.done())

That's really a beautiful and very smart code indeed!