Handling File Inputs With Busboy in NodeJS

February 11, 2023 · 6 min read

Software Developer

Explore how to handle multipart forms in nodeJS with busboy!

In this post, we'll be exploring how to parse multipart form data in Node.js. We'll be using the busboy module to help us accomplish this! We'll also be using the file system module to save the file to your device.

Getting Started

In an empty folder run the following command to create a package.json file

npm init -y

Then run the following command to initialize a git repository

git init

Create a .gitignore file and add the following line to it. This will tell git to ignore the node_modules folder when we push it to our repository.

node_modules

Finally, run the following command to install the busboy module which we'll be using to parse the form data

npm install busboy

Inside the folder you created, create a file called index.js and one called index.html and open them in your favorite text editor...

Writing the HTML

Here's what your index.html file will look like. On the form the action attribute is set to the url of the server we'll be creating. The method is set to POST and the enctype is set to multipart/form-data. This is what tells the browser to send the form data as a multipart request that can be parsed by busboy.

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Node Busboy</title>
  </head>

  <body>
    <form
      action="http://127.0.0.1:3000"
      method="post"
      enctype="multipart/form-data"
    >
      <label for="name">
        Name
        <input type="text" name="name" />
      </label>

      <label for="email">
        Email
        <input type="text" name="email" />
      </label>

      <label for="file">
        File
        <input type="file" name="file" />
      </label>

      <button type="submit">Submit</button>
    </form>
  </body>
</html>

Here's what the form will look like in the browser

form

Writing the Code

Here's what your package.json will look like after installing busboy

{
  "name": "busboy-node",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "busboy": "^1.6.0"
  }
}

Now we'll import the busboy module along with some other packages for our server and handling the file system

// index.js

const http = require("http");
const fs = require("fs");
const os = require("os");
const path = require("path");
const busboy = require("busboy");

Then we'll set the host and port for our server

// index.js

const hostName = "127.0.0.1";
const port = 3000;

Now that we have all of our dependencies and variables set up, we can create our server. Here's a play-by-play of what's happening in this code block:

We create a server with the http.createServer method
We set the Content-Type header to text/plain. This is what we'll be sending back to the client
We check if the request method is POST. If it is, we'll parse the form data with busboy
If the form data is a file, we'll get the filename, encoding and mimeType from the info object
We set the path to save the file. For me, that was my home directory + /Downloads but you can change it to whatever you want/need.
We save the file to the path we set in step 5
If the form data is a field, we'll log the name and value of the field
Finally, we pipe the request to busboy to parse the form data

// index.js

const server = http.createServer((req, res) => {
  res.setHeader('Content-Type', 'text/plain');

  if (req.method === 'POST') {
    const bb = busboy({ headers: req.headers });
    bb.on('file', (name, file, info) => {
      // destructuring the info object to get the filename, encoding and mimeType
      const { filename, encoding, mimeType } = info;
      console.log(
        `File [${name}]: filename: ${filename}, encoding: ${encoding}, mimeType: ${mimeType}}`);

      // set the path to save the file
      const saveTo = path.join(`${os.homedir()}/Downloads`, `${filename}`);

      console.log(`File [${name}] is saving to ${saveTo}`)

      // save the file
      file.pipe(fs.createWriteStream(saveTo));

      file.on('data', (data) => {
        console.log(`File [${name}] got ${data.length} bytes`);
      }).on('close', () => {
        console.log(`File [${name}] done`);
      });
    });
    bb.on('field', (name, val, info) => {
      console.log(`Field [${name}]: value: `, val);
    });
    bb.on('close', () => {
      console.log('Done parsing form!');
      res.end('Done parsing form!');
    });

    // pipe the request to busboy to parse the form data
    req.pipe(bb);
  }

Now we'll listen on the port we set earlier

// index.js

server.listen(port, hostName, () => {
  console.log(`Server running at http://${hostName}:${port}/`);
});

Testing it Out

Now that we have our server set up, we can test it out. Run the following command to start the server

node index.js

Then find the index.html file in your file system and open it in your browser. Fill out the form and click submit, which will present you will the following view in your browser.

done-parsing

In your terminal, you should see the following output along with a bunch of other logs from busboy. You'll also see the file you uploaded in your Downloads folder.

Server running at http://127.0.0.1:3000/
File [avatar]: filename: test.png, encoding: 7bit, mimeType: image/png
Field [name]: value: Mitchell
Field [email]: value: mitchell@email.com
Done parsing form!

You can alternatively open the index.html file by running the following command

open index.html

Alternative HTML Form

Instead of creating an HTML file you could also handle a GET request on the server and send back an HTML form. Here's what the code would look like. You would put this after the if statement that checks if the request method is POST

// index.js

else if (req.method === 'GET') {
    res.statusCode = 200;
    res.setHeader('Content-Type', 'text/html');
    // send a form with a two text inputs and one file input
    res.end(`
      <form action="/" method="post" enctype="multipart/form-data">
        <input type="text" name="name" placeholder="name">
        <input type="text" name="email" placeholder="email">
        <input type="file" name="avatar">
        <button type="submit">Submit</button>
      </form>`);
  }

Conclusion

In this tutorial, we learned how to use busboy to parse form data in Node. We also learned how to save files to the file system.

If you have any questions or comments, feel free to reach out to me on Twitter @mitchelldirt or by email at developer@mitchellmudd.dev

Thanks so much for reading! 🎉

Resources

The repository for this tutorial is here
This Net Ninja Series on how streams and buffers work in Node is fantastic. The whole series is great if you are interested in learning more about Node.

Here's a reference to unix terminal commands that you can use to navigate your file system and more. Unix Commands
The Busboy Documentation is great. It's actually where I got most of the javascript code for this tutorial.
Node's API documentation is great to keep on hand. Just make sure you pick the right version to view haha. Node API Documentation
Learn more about forms on MDN using the MDN Forms series.

Getting Started​

Writing the HTML​

Writing the Code​

Testing it Out​

Alternative HTML Form​

Conclusion​

Resources​