sum(1)(2)(3)() - sum curry recursive like

another.js

function sum(a) {
  if(a == null) return 0 

  return b => b == null ? a : sum(a + b)
}

/*
sum() // 0
sum(1) // 1
sum(1)(2)() // 3
sum(1)(2)(3) // 6
*/

index.js

// my peer ananto pointed out that we can't easily use typescript on these functions

function sum(v) {
  if(v === undefined) {
    return 0
  }

 	let total = v;

  const fn = (val) => {
    if(val === undefined) {
      return total
    }
    else {
      total += val;
      return fn
    }
  }
  
  return fn
}

console.log(sum(2)(3)())
console.log(sum(1)(2)())
console.log(sum())