How to Make Your Async JavaScript Function Wait for Completion

Learn how to handle asynchronous functions in JavaScript using `axios` and avoid common pitfalls.
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How to Make Your Async JavaScript Function Wait for Completion

As you dive into the world of JavaScript, especially when working with asynchronous operations, you may find yourself facing a common dilemma: How do you ensure a function waits for another function to complete before executing? This question often surfaces when using libraries like axios for HTTP requests, as they return promises that may not resolve in the order you expect. In this guide, we'll break down a practical example that illustrates this concept and offers clear solutions.

The Problem

Let's say you want to fetch data from a JSON file and subsequently create an HTML table using that data. Consider this initial implementation:

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

When you run this code, you may notice that the table is created before the data fetching operation from axios is complete. Why does this happen? The answer lies in JavaScript's asynchronous nature—you cannot assume that the data will be ready instantly.

The Solution

Using Callbacks

The easiest way to solve this is by leveraging the built-in behavior of promises returned by axios. Instead of returning the shortcuts array immediately, you can call createShortcutsTable inside the promise resolution block:

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

In this case, createShortcutsTable will only be invoked after the data has been successfully fetched, ensuring the right order of operations.

Using Async/Await

If you're keen on using the async/await syntax, which offers a cleaner and more readable approach to handling promises, here's how you'd do it:

First, convert the axiosGetJSON function into an asynchronous function.

Use the await keyword to simplify the fetching operation.

Here's what your refactored code would look like:

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

Key Takeaways

Callback Approach: Directly call createShortcutsTable within the then block of the promise returned by axios, ensuring data is available when you need it.

Async/Await Approach: Use async on the function and await the promise, simplifying the code and allowing for better readability.

Remember, handling asynchronous code correctly is crucial in JavaScript to avoid unexpected behavior or runtime errors.

Conclusion

Understanding how to manage asynchronous functions effectively is a fundamental skill in JavaScript development. Whether you prefer callback structures or the more elegant async/await syntax, both methods will help you ensure your functions operate in the expected sequence.

Now that you're armed with this knowledge, you can confidently manage asynchronous operations in your JavaScript projects!