How to Fix undefined API Data Issues in Express Routes with Async/Await

Learn how to resolve the `undefined` data issue when fetching API data inside your Express routes using async/await patterns.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Fetching API data inside express route returns undefined when using then or await

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Fix undefined API Data Issues in Express Routes with Async/Await

Creating an Express server that fetches data from an external API can sometimes lead to frustrating situations. One common issue developers encounter is having the fetched data return as undefined even when it appears that everything should work correctly. This guide will uncover the problem and walk you through the solution step-by-step.

The Problem

Imagine you are building an Express server that retrieves currency exchange rates from an external API. You have set up a route to fetch these rates using a helper function but are faced with a peculiar problem: while the server is returning a status of 200, the rates data is undefined. The following is a brief overview of the code:

[[See Video to Reveal this Text or Code Snippet]]

Despite your expectations, the API response you are seeing includes only the status, leaving the rates data undefined. The confusion arises from how you're handling the asynchronous fetch operation.

Understanding the Fetch Operation

[[See Video to Reveal this Text or Code Snippet]]

In the example above, api_response is a promise, and the actual data is not resolved before it is being used, leading to rates being undefined.

The Solution

Refactor the Fetch Logic

Replace the part of your fetch function that currently looks like this:

[[See Video to Reveal this Text or Code Snippet]]

with this revised code:

[[See Video to Reveal this Text or Code Snippet]]

The Fixed Code Snippet

Here’s what the complete and fixed function should look like:

[[See Video to Reveal this Text or Code Snippet]]

Key Takeaways

Handle Errors Properly: Make sure to implement error handling in case your API call fails, and log the necessary details to help with debugging.

By understanding how promises work in JavaScript and correctly structuring your asynchronous calls, you can prevent common pitfalls and ensure your application runs smoothly. If you encounter further issues, revisit your promise chaining and make sure you're resolving values correctly before using them!

With these modifications, you should now be able to retrieve your exchange rates without encountering undefined values.