How to migrate to callback nodejs

Question

I need to transform this code into clean code that uses callbacks, because this code does not allow me to use body information elsewhere.

const endpoints = [];

function getDevicesFromPartnerCloud() {
  var options = {
    method: 'GET',
    url: 'https://database-dcda.restdb.io/rest/endpoints',
    headers: {
      'cache-control': 'no-cache',
      'x-apikey': '*****************************'
    }
  };
  request(options, function (error, response, body) {
    var data = JSON.parse(body);
    data.forEach(function(data, index) {
      let endpoint = createSceneEndpoint(data._id, data.name);
      endpoints.push(endpoint);
    });
  });
  return endpoints;
}

Answer 1

I think the cleanest way to do it would be to use a Promise to handle the asynchronous request. One of the most important things to remember is that functions should ideally do only one thing. That way, they are easier to test, reason about, and refactor. I would pull the code that actually makes the request into a separate function and have it return the body, then have your getDevicesFromPartnerCloud call that new function, get the data back, and process it however it wants. Most importantly, this "frees" the data from being stuck in the request callback, because you're wrapping it in a promise, and resolving it when the data is available.

Something like:

const endpoints = [];

function requestDevices() {
  return new Promise(function(resolve, reject) {
    const options = {
      method: 'GET',
      url: 'https://database-dcda.restdb.io/rest/endpoints',
      headers: {
        'cache-control': 'no-cache',
        'x-apikey': '*****************************',
      },
    };

    request(options, function(error, response, body) {
      if (error) {
        reject(error)
      }

      resolve({ response: response, body: body });
    });
  });
}

async function getDevicesFromPartnerCloud() {
  const devicesResponse = await requestDevices();
  const data = JSON.parse(devicesResponse.body);
  data.forEach(function(data, index) {
    const endpoint = createSceneEndpoint(data._id, data.name);
    endpoints.push(endpoint);
  });

  // Do whatever else you need with devicesResponse.body

  return endpoints;
}

If you wanted to go more of an es6 direction, maybe something like

let endpoints;

const requestDevices = () =>
  new Promise((resolve, reject) => {
    request(
      {
        method: 'GET',
        url: 'https://database-dcda.restdb.io/rest/endpoints',
        headers: {
          'cache-control': 'no-cache',
          'x-apikey': '*****************************',
        },
      },
      (error, response, body) => (error ? reject(error) : resolve(body)),
    );
  });

const getDevicesFromPartnerCloud = async () => {
  try {
    const body = await requestDevices();
    const data = JSON.parse(body);
    endpoints = data.map(({ _id, name }) =>
      createSceneEndpoint(_id, name),
    );

    // Do whatever else you need with devicesResponse.body
    // doStuff(body)

    return endpoints;
  } catch (e) {
    console.error(e);
  }
};