Promise + Callback Example

PromiseAsyncCallback.js

// Our example function to create and populate a user on 2 apis.
function createAndPopulateUserObject (successCallback, errorCallback) {
  const A_createUser = mockAPICallPromise({ body: { id: 1 } })

  // Functional programing no no, shouldn't need to update outer scope,
  // but not a lot of options here.
  let A_userID
  let B_userID

  // Create user on API A
  A_createUser.then(resp => {
    A_userID = resp.body.id
    // Create user on API B
    return new Promise((resolve, reject) => {
      mockAPICallPromise({ body: { B_userID: '000001' } })
        .then(resolve) // success, move on
        .catch(error => {
          // error creating on API B
          deleteUserA(A_userID)
          reject(error)
        })
    })
  })
    .then(resp => {
      // Update API A with ID from API B
      B_userID = resp.body.B_userID
      return new Promise((resolve, reject) => {
        mockAPICallPromise({ body: { A_userID, B_userID } })
          .then(resolve) // success, move on
          .catch(error => {
            // error updating API A
            deleteUserA(A_userID)
            deleteUserB(B_userID)
            reject(error)
          })
      })
    })
    .then(resp => {
      successCallback({ A_userID, B_userID })
    })
    .catch(error => errorCallback(error))
}

createAndPopulateUserObject(console.log, console.error)