How to Return Values from Async/Await Functions in Vue Computed Properties

Learn how to effectively manage data in your Vue.js applications using async/await in computed properties, helping you filter results dynamically from API calls.
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Managing Async Operations in Vue.js Computed Properties

In the world of web development, especially with frameworks like Vue.js, handling asynchronous operations can sometimes lead to challenges. A common issue arises when developers try to use async/await functions within computed properties, particularly when the intention is to filter results based on user input in real-time.

In this guide, we’ll explore a scenario where you need to return the value from an async function in a computed property and how to correctly manage that to ensure data is displayed in the user interface.

The Problem: Returning Promises in Computed Properties

Imagine you have a search bar in a Vue.js application, which allows users to filter through a list of names. You're pulling data from an API and using async/await to handle the response. However, since computed properties can't handle promises—only data—you might find that while your data logs correctly, it fails to render in the UI.

Consider the following example:

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

The above code attempts to fetch data inside a computed property, which ultimately leads to an issue because filteredNames will return a promise instead of the expected list of names needed for rendering. This approach is not only incorrect but inefficient, especially when you're repeatedly calling the API for filtering.

The Solution: Store API Data and Filter Locally

Instead of fetching data each time you need to filter results, a more efficient approach is to store the entire dataset after the initial API call. You can then use a computed property to filter through this local data based on user input.

Here’s how you can implement it:

Step 1: Store API Data

First, we'll create a data property to hold our API data. This property will be populated after making the API call.

Step 2: Filter Locally in Computed Properties

Next, we will set up the computed property to filter through the stored data instead of calling the API each time.

Complete Example

Putting it all together, your Vue.js component could look like this:

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

Breakdown of the Code:

Data Setup:

allItems: This array will hold all the names fetched from the API.

filterText: This string binds to the input field and captures user input dynamically.

Computed Properties:

filteredItems: This computed property returns the names that include the current filterText, enabling live filtering as the user types.

API Call:

The data fetching occurs within the mounted() lifecycle hook. This ensures that the API is called once when the component loads, and the results are stored for further operations.

Conclusion

Using async/await in computed properties directly can lead to complications in Vue.js applications, especially when working with asynchronous data. By storing your results from an initial API call and then filtering that local data in the computed properties, you can handle user input efficiently.

This method not only improves performance by reducing unnecessary API calls but also provides a better user experience by ensuring data renders dynamically.

Give this approach a try in your next Vue.js project and enjoy smoother, more responsive applications!

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