Data undefined in Async data return

Question

I've a problem with a return data from an async function located in Controller file.
I would to get my data in "let data", but it is undefined, I can't understand where is my error..
(of course in my concept of async functions :) )

Here my example:

// index.js
const DataController = require('../controllers/DataController');

router.get('/test', function (req, res, next) {

  let data = DataController.getData().then((resp) => {
    console.log(resp); // <-------- here is undefined

  });
});

// DataController.js
const axios = require('axios').default;
exports.getData = async function getData() {
        return axios.get("https://it.lipsum.com/")
            .then((response) => {
                // console.log(response)
                return response;
            })
            .catch(function (error) {
                // handle error
                console.log(error);
            })
            .then(function () {
                // always executed
            });
    }

Does this answer your question? [How do I return the response from an asynchronous call?](https://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call) — Liam, May 11 '21 at 13:57
`.then(function () { // always executed });` what is the code here? — VLAZ, May 11 '21 at 13:57
@VLAZ an example of HTTP call from Axios documentation, the code was structured as a paste — Mariano, May 11 '21 at 13:58
and the moral of that story is don't just cut and paste code you don't understand.... — Liam, May 11 '21 at 13:59
This should simply be: `const response = await axios.get("https://it.lipsum.com/");` — Liam, May 11 '21 at 14:00
@RogerAI well, that is the problem. If you have `promise.then().then()` the *second* `.then()` gets its value from the return of the previous `.then()`. So, if you have a `.then()` that doesn't return anything before yours, you get `undefined`. — VLAZ, May 11 '21 at 14:01

Ayzrian · Answer 1 · 2021-05-11T14:10:50.570

0

You need to return the data from the then call.

// DataController.js
const axios = require('axios').default;
exports.getData = async function getData() {
        return axios.get("https://it.lipsum.com/")
            .then((response) => {
                // console.log(response)
                return response;
            })
            .catch(function (error) {
                // handle error
                console.log(error);
            })
            .then(function (res) {
                // always executed
                return res;
            });
    }

The way it works that the Promise always returns the last value .then call returned, so your last .then call was returning then undefined.

Small note about let data = because the call is async you will see Promise not the data the promise will resolve to. You can use async/await syntax in the following way.

router.get('/test', async function (req, res, next) {

  let data = await  DataController.getData();
});

edited May 11 '21 at 14:10

answered May 11 '21 at 14:08

Ayzrian

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There is no point in returning the same result twice – Liam May 11 '21 at 14:09
i was already tried this solution, but not working. I've used the @Liam const resp = axios.get(); and in first page .then( (resp) => console.log(resp) ); That work like a charm – Mariano May 11 '21 at 14:11
Yep, there is no point. I just describe the problem with the current code, and why this does not work. – Ayzrian May 11 '21 at 14:11

score 0 · Answer 2 · answered May 11 '21 at 14:32

Refactor your files like this:

index.js

// index.js
const { getData } = require('../controllers/DataController');

router.get('/test', async (req, res, next) => {
  try {
    let data = await getData();
    console.log(data);
    return res.status(200).json(data);
  } catch (error) {
    console.log('ERROR: ', error);
    return res.status(400).json({
      success: false,
      error
    });
  }
});

DataController.js

const axios = require('axios').default;

const getData = async () => {
  try {
    let response = await axios({
      method: 'get',
      url: "https://it.lipsum.com/"
    });
    return response
  } catch (error) {
    return error;
  }
}

module.exports = { getData };

Data undefined in Async data return

2 Answers2