then-busboy

then-busboy

Promise-based wrapper around Busboy. Process multipart/form-data content and returns it as a single object.

Note: The current documentation is for 2.x version of then-busboy. If you're looking for a previous version, check out the 1.x branch.

Installation

You can install then-busboy from npm:

npm install --save then-busboy

Or with yarn:

yarn add then-busboy

API

busboy(request[, options]) -> Promise<object>

• http.IncomingMessage request – HTTP request object
• object options
  • boolean restoreTypes – allow to restore type of each value (default – true)
  • more information about busboy options here.

constructor File(options)

• object options – an object that contains the following information about file:
  • stream.Readable contents – the content of the file.
  • string filename – name of the file (with an extension)
  • string env – encoding of the file content
  • string mime – file mime type

Instance properties

contents

File contents Readable stream.

stream

Alias for contents

filename

Full name of the file

basename

Name of the file without extension

extname

File extension

mime

File mime type

enc

File contents encoding

path

Default path of the file

Instance methods

read() => Promise<Buffer>

Read a file from contents stream.

write([path]) => Promise<void>

Write a file content to disk. Optionally you can set a custom path.

• string path – a path where File content should be saved. (default – File#path)

By default, file will be saved in system temporary directory os.tmpdir(). You can take this path from path property.

isFile(value) -> boolean

Check if given value is a File instance.

• any value – a value to verify

Fields format

then-busboy can restore an object structure from form-data field names if you will follow the special naming format with bracket notation:

# Note that the following example is just a pseudo code
rootField[nestedField] = "I beat Twilight Sparkle and all I got was this lousy t-shirt"

then-busboy will return the this object for an example from above:

{
  rootField: {
    nestedField: "I beat Twilight Sparkle and all I got was this lousy t-shirt"
  }
}

You can also send an arrays and collections using bracket format:

message[sender] = "John Doe"
message[text] = "Some whatever text message."
message[attachments][0][file] = <here is the file content>
message[attachments][0][description] = "Here is a description of the file"

then-busboy returns the following object:

{
  message: {
    sender: "John Doe",
    text: "Some whatever text message.",
    attachments: [
      {
        file: File, // this field will be represended as a File instance
        description: "Here is a description of the file"
      }
    ]
  }
}

Note that there is no an implementation for array as root field for now!

Usage

then-busboy works fine even with a pure Node.js HTTP server. Let's take a look to the tiny example:

import busboy from "then-busboy"
import {createServer} from "http"

function handler(req, res) {
  // Get result from then-busboy
  function onFulfilled(body) {
    res.writeHead("Content-Type", "application/json")

    // You can also do something with each file and a field.
    res.end(JSON.stringify(body))
  }

  // Handle errors
  function onRejected(err) {
    res.statusCode = err.status || 500
    res.end(String(err))
  }

  // Call `then-busboy` with `req`
  busboy(req).then(onFulfilled, onRejected)
}

createServer(handler)
  .listen(2319, () => console.log("Server started on http://localhost:2319"))

Note: You can use asynchronous function syntax, because then-busboy always returns a Promise.

So, let's see on a simple middleware example for Koa.js:

import busboy from "then-busboy"

const toLowerCase = string => String.prototype.toLowerCase.call(string)

const multipart = () => async (ctx, next) => {
  if (["post", "put"].includes(toLowerCase(ctx.method)) === false) {
    return await next()
  }

  if (ctx.is("multipart/form-data") === false) {
    return await next()
  }

  ctx.request.body = await busboy(ctx.req)

  await next()
}

export default multipart

You can check if some value is an instance of File class using isFile. This function may help you if you're wanted to do something with received files automatically.

import busboy, {isFile} from "then-busboy"

let body = await busboy(request)

body = await deepMapObject(
  body, async val => (
    isFile(val) // check if current element is a File
      ? await processFile(val) // do somethig with a file
      : val // ...or just return a field
  )
)

License

MIT