Introduction to Busboy

Busboy is a high-performance, low-level Node.js module that allows you to process file uploads in a streaming fashion. It is particularly useful for handling large file uploads without using excessive memory resources.

Getting Started with Busboy

First, let’s install the busboy module:

  
    npm install busboy
  

Basic Usage

To use Busboy, you typically set it up as middleware in an Express application:

  
    const express = require('express');
    const Busboy = require('busboy');
    const fs = require('fs');
    const path = require('path');

    const app = express();

    app.post('/upload', (req, res) => {
      const busboy = new Busboy({ headers: req.headers });
      busboy.on('file', (fieldname, file, filename, encoding, mimetype) => {
        const saveTo = path.join(__dirname, 'uploads', path.basename(filename));
        file.pipe(fs.createWriteStream(saveTo));
      });

      busboy.on('finish', () => {
        res.writeHead(200, { 'Connection': 'close' });
        res.end("File uploaded successfully!");
      });

      return req.pipe(busboy);
    });

    app.listen(3000, () => {
      console.log('Server listening on port 3000');
    });
  

Configuring Busboy

Busboy can be configured with several options. Here are some common configurations:

  
    const busboy = new Busboy({
      headers: req.headers,
      highWaterMark: 2 * 1024 * 1024, // Set highWaterMark to 2MB
      limits: {
        fileSize: 10 * 1024 * 1024, // Limit file size to 10MB
        files: 5, // Limit number of files uploaded
      }
    });
  

Handling Errors

Error handling is crucial for robust applications. Here’s how to handle errors in Busboy:

  
    busboy.on('error', (err) => {
      console.error('Error during file upload', err);
      res.writeHead(500, { 'Connection': 'close' });
      res.end("Upload failed!");
    });
  

Storing Files in Memory

Sometimes you may want to store files in memory instead of saving them directly to disk:

  
    busboy.on('file', (fieldname, file, filename, encoding, mimetype) => {
      let buffers = [];
      file.on('data', (data) => {
        buffers.push(data);
      });
      file.on('end', () => {
        const fileBuffer = Buffer.concat(buffers);
        // Do something with fileBuffer, e.g., save to database
      });
    });
  

Saving Metadata

Busboy also allows you to save file metadata, such as the fieldname or mime type:

  
    busboy.on('file', (fieldname, file, filename, encoding, mimetype) => {
      const fileData = {
        fieldname,
        filename,
        encoding,
        mimetype
      };
      // Save fileData to database or process it as needed
    });
  

Real-World Application Example

Let’s create a small application that uses Busboy to upload files, store them in a directory, and return the list of uploaded files:

  
    const express = require('express');
    const Busboy = require('busboy');
    const fs = require('fs');
    const path = require('path');

    const app = express();
    const uploadPath = path.join(__dirname, 'uploads');

    app.post('/upload', (req, res) => {
      const busboy = new Busboy({ headers: req.headers });
      busboy.on('file', (fieldname, file, filename, encoding, mimetype) => {
        const saveTo = path.join(uploadPath, path.basename(filename));
        file.pipe(fs.createWriteStream(saveTo));
      });

      busboy.on('finish', () => {
        fs.readdir(uploadPath, (err, files) => {
          if (err) {
            res.writeHead(500, { 'Connection': 'close' });
            res.end("Failed to list files!");
            return;
          }
          res.writeHead(200, { 'Content-Type': 'application/json' });
          res.end(JSON.stringify({ files }));
        });
      });

      return req.pipe(busboy);
    });

    app.listen(3000, () => {
      console.log('Server listening on port 3000');
    });
  

Conclusion

Busboy is a powerful, efficient, and flexible choice for handling file uploads in Node.js. By leveraging its streaming capabilities, you can build scalable and resource-efficient file upload services.

Happy coding!

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