Converting an async Function to a Promise-Based Function Using Promise Chaining in JavaScript

Learn how to convert an async function to a promise-based function using promise chaining in JavaScript without helper methods.
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How to Convert an async Function to a Promise-Based Function in JavaScript

JavaScript developers often use async and await for handling asynchronous operations, which allow us to write code that appears synchronous. However, there might be situations where you need to convert an async function into one that uses promises directly, without any helper functions. In this article, we will discuss how to effectively achieve this by using promise chaining.

Understanding the Problem

Consider you have an async function that retrieves user profile data and repositories from the GitHub API. Here's what the original async function looks like:

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

This function beautifully utilizes await to fetch data, but for various reasons, like browser compatibility, you may need to rewrite this function using promise chaining instead of async/await syntax. Let's see how we can do this.

Converting the Function to Use Promise Chaining

To convert the async function into a promise-based function, we can leverage .then() calls. Here’s the transformed version of the getUser function:

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

Breakdown of the Code

Here's a quick overview of how the conversion works:

Fetching User Profile:

We begin by using fetch to get the user profile using the provided username.

The first .then() handles the response and calls the json() method to parse the data.

Fetching User Repositories:

After fetching the profile data, the second .then() handles this data and makes another fetch request to get the repositories for the user.

Returning Data:

Finally, we chain a third .then() that parses the repositories’ data and returns an object containing both the profile data and the repositories.

Important Note

While converting async functions to promise-based functions using direct promise chaining works, it's essential to consider code readability. For simple scenarios, the transformation is straightforward, as detailed. However, if your function involves more complex logic, using async/await might be a cleaner choice.

If you're targeting an environment that doesn't support async/await, a transpiler (like Babel) can handle these conversions for you automatically. This can keep your code neatly written in modern JavaScript without unnecessary complications.

Conclusion

In this article, we learned how to convert an async function that retrieves user data from the GitHub API into a function that employs promise chaining. By utilizing .then() calls, we achieved the same functionality while adhering to the promise-based syntax. This knowledge can be particularly useful when dealing with browser compatibility issues or when integrating with systems where you might need to conform to specific coding standards.

For more hands-on experience and JavaScript tips, be sure to explore additional resources or dive into more complex asynchronous patterns to continue honing your skills!