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

Here is a solution that uses ES6 and toString, similar to @Vemba

function add(a) {
  let curry = (b) => {
    a += b
    return curry
  }
  curry.toString = () => a
  return curry
}

console.log(add(1))
console.log(add(1)(2))
console.log(add(1)(2)(3))
console.log(add(1)(2)(3)(4))