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

New ES6 way and is concise.

You have to pass empty () at the end when you want to terminate the call and get the final value.

const sum= x => y => (y !== undefined) ? sum(x + y) : x;

call it like this -

sum(10)(30)(45)();