Solving the Await Doesn't Do the Job Problem in JavaScript: A Guide to Using Async/Await Correctly

Discover how to fix the issue where `await` doesn’t work as expected in your JavaScript async functions. Learn the correct usage of reduce with promises, and optimize your image upload handling.
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Understanding the Issue: Why Await Isn't Working

In the world of JavaScript, specifically when dealing with asynchronous operations, developers often encounter the perplexing problem of the await keyword not behaving as expected. This issue can be particularly noticeable when using array methods like .map() and .reduce() in conjunction with promises. If you’ve ever found that your asynchronous code doesn’t seem to produce the results you were expecting despite using await, you’re not alone. In this post, we’ll break down a concrete example of this problem and walk through the solution step by step.

The Problem Scenario

Imagine you have the following code attempting to map through an array of folders, uploading images and returning their URLs:

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

As a result, you might be getting output that looks like this:

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

However, instead of multiple image URLs, you only capture the first image in your output. Utilizing an await inside reduce isn’t functioning correctly, leading to confusion.

Breaking Down the Solution

After diving into research and trial error, it became evident that the way reduce() interacts with promises was the root cause of the issue. Here's how to effectively manage asynchronous operations using reduce().

The key to solving this problem is realizing that reduce() potentially returns only a single promise. To handle multiple promises correctly, we need to use an initial resolved promise and chain subsequent promises onto it. Here's a clear example of how to accomplish this:

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

How This Works

Chaining Promises: Inside reduce(), each element is processed sequentially. The promise returned by the acc results in fetching data asynchronously without blocking the next calls.

Final Result: Once all promises have been resolved, you can await postsPromise to get the final structured result.

Implementing the Solution

To apply this to your original image upload scenario, you can rewrite your function to properly handle the image URLs using the above structure:

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

Conclusion

Remember, the key takeaway is to use an initial resolved promise that allows you to build on successively while awaiting the results of operations—making your code cleaner and more reliable.

Now you can confidently tackle any challenges with await and async functions in JavaScript!