Variadic curried sum function

Question

I need a js sum function to work like this:

sum(1)(2) = 3
sum(1)(2)(3) = 6
sum(1)(2)(3)(4) = 10 
etc.

I heard it can\'t be done. But heard

Answer 1

let add = (a) => {
  let sum = a;
  funct = function(b) {
    sum += b;
    return funct;
  };

  Object.defineProperty(funct, 'valueOf', {
    value: function() {
      return sum;
    }
  });
  return funct;
};


console.log(+add(1)(2)(3))