Скачать или смотреть How to Upload Multiple Images Using Blob to Your Server with React and Express

Learn how to efficiently upload multiple image files using blobs in your website built with React, Express, and Next.js. Fix common issues and ensure successful uploads.
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This video is based on the question https://stackoverflow.com/q/76471191/ asked by the user 'Senior Coder' ( https://stackoverflow.com/u/21984019/ ) and on the answer https://stackoverflow.com/a/77068934/ provided by the user 'Takao Miyazaki' ( https://stackoverflow.com/u/22068494/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Uploading Multiple Images Using Blob to the Server

In the realm of web development, creating a seamless experience for users is paramount. One common feature that web applications often require is the ability to upload multiple images. However, if you've been working with blobs in React and encounter errors when attempting to upload multiple files, you're not alone.
Let's break down the problem and walk through a solution step-by-step.

Understanding the Problem

You might already have a setup where you can successfully upload a single image to your server using blobs, but when it comes to multiple files, things take a turn for the worse. This issue could be due to mishandled data during the upload process on the client-side or the server-side. In this guide, we will examine both parts and how to ensure our implementation works flawlessly.

The Current State

You have implemented a React state to manage the images as blobs:

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

You also have a submission handler that collects the image blobs and appends them to a FormData object for submission to the server.

Despite this correct configuration for single file uploads, when it comes to multiple files, your server-side code is returning undefined properties upon checking if multiple files were uploaded. This is a common stumbling block and can usually be resolved with a few key adjustments.

Step-by-Step Solution

Let's delve into some of the adjustments you'll need to make on both the client and server sides.

Client-Side Code Review

Ensure Blob Management: Verify that you're correctly setting blobs into the state and that the blobs array gathers all selected files.

Construct FormData: In your handleAdd function, make sure that you are appending the blobs correctly using a loop. You're already using Object.values(blobs).filter(val => val !== null) correctly to append only non-null blobs.

Server-Side Code Adjustments

Review req.files Handling: On the server-side, you should ensure that your setup can handle multiple file uploads. The key piece of code here checks if multiple images are present:

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

Check for Bugs: If you log req.files and find unexpected results, you may have a misconfiguration in your file upload middleware. Ensure you are using a middleware package such as multer configured for handling multiple files.

Configuring propertyName in nuxt.config.js: As mentioned in your question, if you're using Nuxt.js, make sure your propertyName in the authentication strategies is set correctly. It should bypass default checks if the response structure from the endpoint doesn't match expected values:

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

Final Thoughts

Debugging multiple file uploads can be tricky, but with meticulous verification of both client and server-side configurations, you should be able to create a fail-proof image upload feature for your website. Ensure you test each part of the flow and confirm that blobs are being handled correctly.

By following this guide, not only will you resolve the issue when uploading multiple images, but you’ll also gain a deeper understanding of managing uploads in your application. Happy coding!