Variable scope issue with Firebase Functions and social media API integration

Other Questions API
1

Need help with variable scope in Firebase Cloud Functions

I’m working on a Firebase function that fetches data from a social media API and returns it as an HTTP response. The API call works fine and I can see the data in the console logs, but I’m having trouble with variable scope in JavaScript.

The main issue is that I can’t figure out how to get the data from inside the API callback and use it in the outer function scope to send back as the Firebase response.

exports.socialMediaHandler = functions.https.onRequest((req, res) => {

  const apiClient = new SocialAPI({
    api_key: "your_key_here",
    api_secret: "your_secret_here",
    token: "your_token_here",
    token_secret: "your_token_secret_here"
  });

  const queryParams = { username: "testuser" };
  let fetchedData = "";

  apiClient.fetch("posts/recent", queryParams, (err, posts, apiResponse) => {
    if (err) throw err;
    fetchedData = posts[0].content;
    console.log(posts[0].content);
    console.log(fetchedData);
    res.send(fetchedData); // Send response inside callback
  });

});

How can I properly handle the asynchronous callback and pass the data to the response?

2

your code looks fine, sending the response in the callback is exactly how you should handle this async pattern. this isn’t a scope problem, just normal js callback behavior. i’d check if your api calls are actually going through and watch for any network timeouts that might be causing problems.

3

Your callback approach is outdated and makes scope management way too complex. Most modern APIs support promises, so check if your SocialAPI library has promise support or use Node’s util.promisify. Here’s how I handled something similar with a Twitter API:

const { promisify } = require('util');

exports.socialMediaHandler = functions.https.onRequest(async (req, res) => {
  try {
    const apiClient = new SocialAPI({
      api_key: "your_key_here",
      api_secret: "your_secret_here",
      token: "your_token_here",
      token_secret: "your_token_secret_here"
    });
    
    const fetchAsync = promisify(apiClient.fetch.bind(apiClient));
    const queryParams = { username: "testuser" };
    
    const [posts, apiResponse] = await fetchAsync("posts/recent", queryParams);
    const fetchedData = posts[0].content;
    
    res.send(fetchedData);
  } catch (error) {
    console.error(error);
    res.status(500).send('Error fetching data');
  }
});

This completely eliminates the scope issue by converting the callback to a promise and using async/await.

4

Your callback structure looks right for async operations, but there’s a major error handling issue that’s probably causing silent failures. Don’t use throw err inside callbacks - Firebase won’t catch those errors. You need to send proper error responses instead.

I hit this same problem integrating Instagram’s API last year. Fix your error handling like this:

apiClient.fetch("posts/recent", queryParams, (err, posts, apiResponse) => {
  if (err) {
    console.error('API Error:', err);
    return res.status(500).send('Failed to fetch social media data');
  }
  
  if (!posts || posts.length === 0) {
    return res.status(404).send('No posts found');
  }
  
  const fetchedData = posts[0].content;
  res.send(fetchedData);
});

Also throw in a timeout mechanism - social media APIs can be flaky. The scope isn’t your problem here, it’s the error flow breaking your function silently.