In response to https://t.co/KlxtCtCDJ4

original.js

// promise code
function add5 (x) {
  return x + 5
}

function add5Promise (x) {
  return Promise.resolve(x).then(function (x) {
    return add5(x)
  })
}

function someNumberLater () {
  return new Promise(function (resolve) {
    databaseConnector.get('numeric value').then(function (x) {
      resolve(x)
    })
  })
}

add5Promise(someNumberLater()).then(function (xplus5) {
  console.log('the number plus 5 is %d', xplus5)
})

simplified.js

function add5 (x) {
    return x + 5
}

function someNumberLater () {
    // if you are unsure what kind of thenable this returns and you want clear API,
    // you could wrap in Promise.resolve()
    return databaseConnector.get('numeric value');
}

someNumberLater().then(add5).then(function (xplus5) {
    console.log('the number plus 5 is %d', xplus5)
});