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A comprehensive guide to resolving the issue of undefined return values in Javascript's async/await functions. Learn how to correctly handle promises for clear and efficient code.
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Understanding Why Javascript async/await Can Return undefined

If you've been working with JavaScript's async/await syntax to handle asynchronous tasks, you might have encountered an issue where your function appears to return undefined. This often happens in scenarios like API calls where you're trying to retrieve a value after a data post.

In this post, we'll break down a common issue related to the async/await function and how to properly work with promises to ensure you don't get unexpected undefined results.

The Problem: Why Is the Return Value Undefined?

Consider the following scenario: you have an asynchronous function, postAsset, that posts data to an API and you're trying to retrieve the response. Despite following various guides, your attempt yields undefined when trying to access the return value of this function.

An example piece of code looks like this:

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

The return from the function might be always undefined due to a misunderstanding of promise handling in JavaScript, particularly when mixing await with .then().

The Solution: Proper Handling of Promises

There are two approaches you can take to resolve the undefined return issue in an async function:

Solution 1: Return the Promise from the axios.post

To retain the correct flow of values, it's necessary to return the promise you obtain from axios.post. You just need to add return before the axios.post() call:

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

This makes sure that the postAsset function returns the entire promise chain correctly.

Solution 2: Use async/await Consistently (Recommended)

A cleaner and more effective approach is to avoid using .then() entirely in an async function. Instead, you can wait for the promise to resolve directly with await, which leads to clearer and more readable code.

Here's how you can refactor the code:

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

In this version:

The await keyword pauses the function execution until the promise resolves.

It allows direct access to the response, making error handling straightforward.

By simplifying your approach and not mixing .then with async/await, you not only avoid the undefined return issue but also create a more maintainable codebase.

Conclusion

Understanding how JavaScript handles promises with async/await is crucial for effective coding practices. By following the solutions outlined above, you can ensure that your functions return the expected values without facing the dreaded undefined.

If you come across issues like this, remember to check if you're properly returning the results from your promise-chain and try to keep your code consistent with either .then() or await.

Now, go ahead and give your code a check! Happy coding!