Instead of writing nested callbacks, we can write Promise (natively available from Node 4) calls.

nodejs-promise.js

// ❌
asyncFunc1((err, result1) => {
  asyncFunc2(result1, (err, result2) => {
    asyncFunc3(result2, (err, result3) => {
      console.log(result3)
    })
  })
})

// ✔️

asyncFuncPromise1()
  .then(asyncFuncPromise2)
  .then(asyncFuncPromise3)
  .then((result) => console.log(result))
  .catch((err) => console.error(err))