How to Properly Use await inside a Promise in JavaScript

Discover how to effectively handle asynchronous requests in JavaScript by using `await` within promises. Avoid common pitfalls and learn by example!
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How to Properly Use await inside a Promise in JavaScript

When working with JavaScript, especially with asynchronous code, you may find yourself needing to use the await keyword inside a promise. This might seem straightforward, but there are specific patterns and structures in JavaScript that you must follow to avoid common errors. In this post, we will explore the problem of using await within a promise and break down the solutions step-by-step to ensure you can implement it efficiently in your projects.

The Problem: When and Why Do You Need await?

Imagine you are making requests to a server, but the server requires authentication to process these requests. For example, if you need to add an access token to every request, you would normally have to await the promise that retrieves the token before sending your requests.

Initially, you might have a structure that looks like this:

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

However, this construct has a flaw; specifically, you get an error when trying to use async inside the promise executor. The error message reads: "Promise executor functions should not be async (no-async-promise-executor)."

The Solution: Restructuring Your Code

To resolve this dilemma, you will need to refactor your code to ensure that await operates correctly without falling into the pitfalls of promise executors. Here's how you can revise your method to make it more efficient:

Refactoring Step by Step

Make the function async: Change the countries function to an async function so that you can use await directly inside it.

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

Get the Access Token: Call the addAccessToken() function to obtain the token before proceeding with making the requests.

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

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

Updated Code Example

Here’s your updated countries function:

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

Using the Responses

Now, to handle the results from multiple requests, you could use it like this:

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

Conclusion: Cleaner Code with async/await

With these adjustments in mind, you can confidently work with JavaScript promises and asynchronous requests while ensuring your code remains clear and maintainable.