Introduction to Busboy

Busboy is a fast and robust module designed to parse incoming form data, especially file uploads, in Node.js applications. Built on top of the dicer parser, its efficiency makes it an excellent choice for handling multipart form data.

Installing Busboy

First, you need to install the Busboy package:

npm install busboy

Using Busboy: Basic Example

Here’s a basic example showing how to use Busboy to handle file uploads:

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

const server = http.createServer((req, res) => {
  if (req.method === 'POST') {
    const busboy = 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');
    });

    req.pipe(busboy);
  } else {
    res.writeHead(404);
    res.end();
  }
});

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

Busboy API Methods

Busboy offers several useful methods for handling different aspects of file and form data uploads:

Busboy#Field

The field event handles non-file fields in the form. Example:

busboy.on('field', (fieldname, val, fieldnameTruncated, valTruncated, encoding, mimetype) => {
  console.log(`Field [${fieldname}]: value: %j`, val);
});

Busboy#File

The file event handles file streams. Example:

busboy.on('file', (fieldname, file, filename, encoding, mimetype) => {
  const saveTo = path.join(__dirname, 'uploads', path.basename(filename));
  file.pipe(fs.createWriteStream(saveTo));
});

Busboy#PartsLimit

Limit the number of fields and files being parsed.

const busboy = new Busboy({
  headers: req.headers,
  limits: {
    parts: 10, // Max number of parts (fields/files)
  }
});

Busboy#FilesLimit

Limit the number of file fields being parsed.

const busboy = new Busboy({
  headers: req.headers,
  limits: {
    files: 1, // Max number of file fields
  }
});

Busboy#FieldsLimit

Limit the number of fields (excluding files) being parsed.

const busboy = new Busboy({
  headers: req.headers,
  limits: {
    fields: 5, // Max number of non-file fields
  }
});

Building an App with Busboy

Let’s create a basic app with the mentioned APIs. The app will handle file uploads and display form field data:

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('field', (fieldname, val) => {
    console.log(`Field [${fieldname}]: value: %j`, val);
  });

  busboy.on('finish', () => {
    res.writeHead(200, { 'Connection': 'close' });
    res.end('Upload complete');
  });

  req.pipe(busboy);
});

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

With this setup, the server will be able to handle file and field uploads gracefully while enforcing the specified limits.

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