Ensuring Ordered Responses in React: Fetching Images as Base64 Strings with async/await

Learn how to efficiently fetch images using a `for` loop in React, convert them to Base64, and ensure the order of responses using `async/await`.
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Ensuring Ordered Responses in React: Fetching Images as Base64 Strings with async/await

When building web applications using React, developers often need to fetch images, convert them to Base64 format, and store them in an array. The problem arises when multiple asynchronous fetch requests are made in a loop. Each fetch request can return its response at a different time, potentially causing the order of the array to get jumbled. In this guide, we’ll explore a solution to maintain that order by using async/await for fetching images, and we’ll provide a step-by-step guide to achieve this.

The Problem

In a typical scenario, you might have a list of file paths for images that you want to convert to Base64 and store in an array. In the example you might have:

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

The challenge here is to ensure that when you fetch these images and convert them to Base64, they remain in their original order within the targetlist state. As each fetch request may take a different amount of time to complete, the responses may come back out of order, leading to a jumbled targetlist.

The Solution: Using async/await

To solve this problem, we can use the async/await syntax, which helps us avoid the “callback hell” and better control the flow of asynchronous operations. Here’s how you can implement it.

Step 1: Convert the getTarget Function to Async

We’ll transform the getTarget function into an asynchronous function. This allows us to wait for each fetch to complete before proceeding to the next image.

Here’s the modified function:

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

Step 2: Breakdown of the Code

Async Function Declaration: By marking the function with async, we can use the await keyword inside it.

Loop Through File Paths: We still use a for loop to iterate through the file paths. This way, we maintain the order of operations.

Awaiting the Fetch: Instead of handling fetch-response with .then(), we await the result. This means the code will pause at this point until the fetch is complete and we have the blob data.

Reading Blob as Data URL: The FileReader is used to convert the blob into a Base64 string. When it's done, the onloadend event is triggered, where we update the state.

Updating State: We concatenate the new Base64 string to the targetlist in the state using an updater function to avoid conflicts.

Benefits of This Approach

Guaranteed Order: Using async/await ensures that each image is processed one after the other, preserving their order.

Readability: The code is easier to read and understand compared to deeply nested callbacks or multiple .then() calls.

Simplicity: With this approach, handling errors becomes simpler as you can use try/catch blocks around your await calls.

Conclusion

By using async/await for fetching images in React, you can ensure that they are converted to Base64 and stored in the correct order within your state array. This not only improves the structure of your code but also enhances readability, making it easier to maintain and debug.

Feel free to implement this technique in your projects and experience the seamless handling of asynchronous operations in React!