Compare async performance with sync.

async.js

const fibsync = n => {
  if (n <= 1) return 1
  const a = fibsync(n - 1)
  const b = fibsync(n - 2)
  return a + b
}

const fibasync = async (n) => {
  if (n <= 1) return 1
  const a = fibasync(n - 1)
  const b = fibasync(n - 2)
  return await a + await b
}

const doTest = async(n) => {
  console.log("n = ", n)
  console.log("sync start", new Date())
  const ressync = fibsync(n)
  console.log("sync end", new Date())
  console.log("ressync = ", ressync)

  console.log("async start", new Date())
  const resasync = await fibasync(n)
  console.log("async end", new Date())
  console.log("resasync = ", resasync)
}

doTest(28)