infinite function call: Sum(a)(b,c)...(x,y,z) => a + (b + c) + ... + (x + y + z)

infinity-sum.js

function sum(...args) {
  let total = 0;

  const reduceSum = (arr = [], start = 0) => {
    return arr.reduce((memo, val) => memo + val, start);
  };

  const fn = (...args) => {
    const newSum = reduceSum(args, total);
    total = newSum;

    return fn;
  };

  fn.valueOf = () => total;

  return fn(...args);
}