Implementing a file uploader with suspense in React

16 Oct 2023

In this article, we will explore how to implement a file uploader component using the new React Suspense feature. Suspense allows us to handle components that have asynchronous dependencies, such as data fetching or file uploading, in a more elegant and streamlined way.

Introduction
Prerequisites
Setting up the file uploader component
Implementing the file upload logic
Displaying the file upload progress
Conclusion

Introduction

With the introduction of React Suspense, handling asynchronous operations in React has become much easier. Suspense allows us to suspend rendering until all the required data or resources are available, without the need for complex state management or loading components.

In this tutorial, we will build a simple file uploader component using the Suspense feature provided by React to handle the asynchronous file upload process.

Prerequisites

Before getting started, make sure you have the following installed:

Node.js and NPM or Yarn
React 16.6 or above

Setting up the file uploader component

First, let’s create a new React component called FileUploader. We will start by creating a basic file input element that allows users to select and upload a single file.

import React from 'react';

const FileUploader = () => {
  const handleFileUpload = (event) => {
    // Handle file upload logic here
  };

  return (
    <div>
      <input type="file" onChange={handleFileUpload} />
    </div>
  );
};

export default FileUploader;

Implementing the file upload logic

To handle the file upload logic, we can use the fetch API to send a POST request to a server endpoint. Let’s update our handleFileUpload function to include the file upload logic.

const handleFileUpload = async (event) => {
  const file = event.target.files[0];
  
  const formData = new FormData();
  formData.append('file', file);
  
  const response = await fetch('/upload', {
    method: 'POST',
    body: formData
  });
  
  const data = await response.json();
  
  console.log('File uploaded successfully:', data);
};

In the code above, we create a new FormData object and append the selected file to it. Then, we make a POST request to /upload endpoint with the FormData as the request body. Finally, we parse the response and log it to the console.

Displaying the file upload progress

To display the file upload progress, we can utilize the fetch API’s UploadProgress event. Let’s update our handleFileUpload function to include a progress bar and update it with the upload progress.

const handleUploadProgress = (event) => {
  const { loaded, total } = event;
  
  const progress = Math.round((loaded / total) * 100);
  // Update the progress bar with the calculated percentage
};

const handleFileUpload = async (event) => {
  // ...
  
  const response = await fetch('/upload', {
    method: 'POST',
    body: formData
  });
  
  const reader = response.body.getReader();
  
  while (true) {
    const { done, value } = await reader.read();
    
    if (done) {
      console.log('File uploaded successfully');
      break;
    }
    
    handleUploadProgress({ loaded: value.byteLength, total: file.size });
  }
};

In the updated code, we listen for the UploadProgress event by utilizing the response.body.getReader() method. Inside the loop, we calculate the upload progress percentage and update it accordingly. Once the upload is complete, we log a success message to the console.

Conclusion

In this tutorial, we implemented a file uploader component using the new React Suspense feature. We covered how to handle the file upload process asynchronously and display the upload progress using the fetch API.

React Suspense simplifies handling asynchronous operations in React by providing an efficient and declarative way to manage dependencies. With Suspense, building complex and asynchronous components, like our file uploader, becomes much easier and more intuitive.

Make sure to check out the official React documentation for more details on using Suspense.

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