asyncRecursive.js

function sumNaive (n, acc = 0) {
  if (n === 0) {
    return acc
  }
  return sumNaive(n - 1, acc + n)
}

// console.log(sumNaive(1000))
// console.log(sumNaive(100000))

function trampoline (fn) {
  return (...args) => {
    let result = fn(...args)

    while (result instanceof Function) {
      result = result()
    }

    return result
  }
}

function sum (n) {
  let baseSum = trampoline(function recursiveSum (m, acc = 0) {
    if (m === 0) {
      return acc
    }
    return () => recursiveSum(m - 1, acc + m)
  })

  return baseSum(n)
}

// console.log(sum(1000))
// console.log(sum(100000))

function asyncTrampoline (fn) {
  return async (...args) => {
    let result = fn(...args)

    while (result instanceof Function) {
      result = await result()
    }

    return result
  }
}

function sumAsync (n) {
  let baseSum = asyncTrampoline(function recursiveSum (m, acc = 0) {
    if (m === 0) {
      return acc
    }
    return () => Promise.resolve(recursiveSum(m - 1, acc + m))
  })

  return baseSum(n)
}

sumAsync(1000).then(x => console.log(x))
sumAsync(100000).then(x => console.log(x))