cuurrying in JS

Currying in JS.js

function sum(...args) {
  let total = 0;
  let adjust = -1
  if (args.length && args[0] === 0) {
    adjust = 0
  }

  function inner(...innerArgs) {
    if (innerArgs.length === 0) {
      return total
    }
    args = [...args, ...innerArgs]
    total = args.reduce((acc, i) => acc + parseInt(i), adjust)
    return inner
  }
  return inner(args)
}
console.log(sum(0,0,0)()) // 0
console.log(sum(0,1)(1)()) // 2
console.log(sum(0,1)(1)(2,3)(2)()) // 9
console.log(sum(0,0)(1)(2,3)(0)()) // 6