Downloading Files from a Node.js Server with Express

Downloading files from a server is a common requirement for many web applications. In this tutorial, we will explore how to download files from a Node.js server using the popular Express framework.

Introduction to Express and File Downloading

Express is a lightweight and flexible Node.js web application framework that provides a lot of built-in functionality for handling HTTP requests and responses. When it comes to downloading files, Express provides several ways to achieve this, including using the res.download() method, setting HTTP headers, and using streams.

Using the res.download() Method

The res.download() method is a convenient way to download files from a server. This method transfers the file at the specified path as an attachment, allowing the client to download it. Here’s an example of how to use this method:

const express = require('express');
const app = express();

app.get('/download', (req, res) => {
  const filePath = `${__dirname}/upload-folder/dramaticpenguin.MOV`;
  res.download(filePath);
});

In this example, the res.download() method is used to download a file named dramaticpenguin.MOV from the upload-folder directory.

Setting HTTP Headers

Another way to download files is by setting the appropriate HTTP headers. The Content-Disposition header is used to specify the filename and the type of attachment (e.g., inline or attachment). Here’s an example:

const express = require('express');
const app = express();
const fs = require('fs');
const path = require('path');

app.get('/download', (req, res) => {
  const filePath = `${__dirname}/upload-folder/dramaticpenguin.MOV`;
  const filename = path.basename(filePath);
  const mimetype = 'video/quicktime';

  res.setHeader('Content-Disposition', `attachment; filename=${filename}`);
  res.setHeader('Content-Type', mimetype);

  fs.createReadStream(filePath).pipe(res);
});

In this example, the Content-Disposition header is set to specify the filename and attachment type. The Content-Type header is also set to specify the MIME type of the file.

Using Streams

Using streams is a more efficient way to download large files, as it allows the file to be sent in chunks rather than loading the entire file into memory. Here’s an example:

const express = require('express');
const app = express();
const fs = require('fs');

app.get('/download', (req, res) => {
  const filePath = `${__dirname}/upload-folder/dramaticpenguin.MOV`;

  fs.createReadStream(filePath).pipe(res);
});

In this example, the fs.createReadStream() method is used to create a readable stream from the file. The stream is then piped to the response object using the pipe() method.

Best Practices

When downloading files from a server, it’s essential to follow best practices to ensure security and efficiency:

• Use the res.download() method or set HTTP headers to specify the filename and attachment type.
• Use streams to download large files to avoid loading the entire file into memory.
• Validate user input to prevent unauthorized access to files.
• Use secure protocols (e.g., HTTPS) to encrypt data in transit.

By following these best practices and using the techniques outlined in this tutorial, you can securely and efficiently download files from a Node.js server using Express.