Understanding Why Your Node.js async/await Is Not Working As Expected

Discover the common pitfalls with `async/await` in `Node.js` and get practical solutions for your Express API.
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Understanding Why Your Node.js async/await Is Not Working As Expected

When developing applications with Node.js, especially those built using Express APIs, you may encounter issues with promises and the async/await syntax. One common problem is related to how promises are managed in asynchronous functions. This guide intends to break down the problem you might be facing and offer a practical solution that will enhance your understanding of asynchronous programming in JavaScript.

The Problem: Unawaited Promises in Your API

Imagine you've set up an Express API that interacts with a Fauna database through a class structure. You have the following structure for your getQuotes method:

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

When you call this method in your server setup, you see the output:

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What's Going Wrong?

The issue here lies in how data is being returned from the getQuotes method and how promises are resolved. Specifically, you’re not returning the promise from the getQuotes function itself; instead, your return statement is only resolving from the inner callback of .then. As a result, the method ends up returning undefined rather than the actual data you intended to return.

The Solution: Properly Returning Values and Using await

To fix this issue, you should modify your getQuotes method to ensure it properly utilizes async/await and returns the correct data. Here’s how you can do that:

1. Return the Promise from getQuotes

Modify your getQuotes function to use the await keyword, which allows you to handle asynchronous calls more elegantly:

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

2. Utilize the await Syntax When Calling getQuotes

When calling getQuotes, make sure to await the result to ensure you have the necessary data before proceeding:

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

Example of Complete Setup

Here's how your Express server might look once you've made the necessary changes:

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Summary

Using async/await effectively can streamline your code and make dealing with asynchronous operations easier. Remember these steps:

Always return the promise from your async functions.

Use await when calling an async function to ensure you get the resolved value.

Take advantage of try-catch blocks around async calls to handle exceptions gracefully.

By implementing these changes, you should find that your async/await is behaving as expected, retrieving the right data from your Fauna database, and avoiding issues with undefined values.

Feel free to share your experiences or any additional queries you might have regarding asynchronous programming in Node.js!