How to Properly Return Values from Promises in JavaScript

Learn how to effectively return values from promises in JavaScript. This post simplifies handling asynchronous operations for better control in your applications.
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Understanding Promises in JavaScript

If you're diving into JavaScript, you might have come across the concept of promises. Promises are a crucial part of managing asynchronous operations, especially when dealing with tasks like fetching data from an API. Many developers, especially those new to JavaScript, encounter challenges when learning how to properly return values from promises.

In this guide, we'll break down how to handle promises effectively, especially in the context of a situation where you need to return an array of objects based on certain conditions — in this case, checking for upcoming birthdays.

The Problem

Imagine you have a simple API that returns an array of people along with their properties, such as first name, last name, and date of birth (d.o.b). Your goal is to find out which of these people have their birthdays within the next 10 days.

You might encounter difficulties when trying to return the results correctly from your promise. Let's see how to simplify this process.

The Initial Attempt

You might start with a structure like this in your API:

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

In this code snippet, the promise isn't resolved appropriately, which can lead to confusion. Let's restructure the code to ensure we handle the promises correctly.

The Proper Solution

Step-by-Step Approach

Here's a clearer implementation that returns the expected results:

Eliminate Unnecessary Promises: Since getNextBirthdays should return an array directly, we don't need to wrap it in a promise.

Use Regular Functions: Instead of an async function for getNextBirthdays, we can use a regular function since we're not using await within it.

Here is the revised code:

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

Key Changes Explained

Directly Return Values: The function getNextBirthdays now returns an array without wrapping it in a promise, simplifying the flow.

Asynchronous Logic: Functions getDaysTillBirthday, birthdayDayOfYear, and dayOfTheYear are no longer declared as async functions because they don't need to be awaited. They operate synchronously within the getNextBirthdays function.

Conclusion

By restructuring your code, you can effectively manage promises and return values in JavaScript. This not only streamlines your application but also enhances readability, making it easier for others (and yourself) to understand.

Leveraging this approach allows you to focus more on the logic of your applications rather than dealing with the intricacies of promise management. Happy coding!