then-busboy
Promise-based wrapper around Busboy. Processes multipart/form-data request body and returns it in a single object.
Installation
You can install then-busboy from npm:
npm install --save then-busboy
Or with yarn:
yarn add then-busboy
Usage
Because then-busboy can process multipart/form-data bodies from AsyncIterable sources, you can use it with different HTTP frameworks, or with Node.js http module, or even with Response object (see the 4th example).
- Let's take a look at the example with
httpmodule from Node.js. We'll write a simple server that will parse form-data request, read files content and then send them back as JSON:
import {createServer} from "http"
import {parse} from "then-busboy"
const handler = (req, res) => parse(req)
.then(async body => {
const result = []
for (const [path, value] of body) {
result.push([path, isFile(value) ? await value.text() : value])
}
res.setHeader("Content-Type", "application/json")
res.end(JSON.stringify(Body.json(result)))
})
.catch(error => {
res.statusCode = error.status || 500
res.end(error.message)
})
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.
- Miniaml multipart middleware implementation for Koa.js:
import {parse} from "then-busboy"
async function multipart(ctx, next) {
if (["post", "put"].includes(ctx.method.toLowerCase()) === false) {
return next()
}
if (ctx.is("multipart/form-data") === false) {
return next()
}
const body = await parse(ctx.req)
ctx.request.body = body.json()
return next()
}
export default multipart- You can also use
AsyncIterablevalue as the input. That way you can parse FormData from other that just HTTP requests. Let's take a loook at the example withform-data-encoderandformdata-nodeas the input:
import {fileFromPath} from "formdata-node/file-from-path"
import {FormDataEncoder} from "form-data-encoder"
import {FormData} from "formdata-node"
import {parse} from "then-busboy"
const form = new FormData()
form.set("greeting", "Hello, World!")
form.set("file", new File(["On Soviet Moon landscape see binoculars through YOU"], "file.txt"))
form.set("fileFromPath", await fileFromPath("path/to/a/file"))
const encoder = new FormDataEncoder(form)
const body = await parse(encoder, {
headers: {
"content-type": encoder.contentType
}
})
console.log(body.json()) // -> {greeting: string, file: BodyFile, fileFromPath: BodyFile}- Because
then-busboyaccepts AsyncIterable as the input, you can also readResponsebody like that:
import {Response, FormData} from "node-fetch"
import {parse} from "then-bosboy"
const form = new FormData()
form.set("greeting", "Hello, World!")
form.set("file", new File(["On Soviet Moon landscape see binoculars through YOU"], "file.txt"))
const response = new Respone(form)
// then-busboy will parse the input and return its own Body instance from which you can create a complete object by calling .json() method or a FormData using .formData() method.
// The difference with Response.formData() is that then-busboy will save all files to file system and create a *reference* to each of them,
// while Response (currently) will dump them into RAM, which can be less efficient in some scenarious
const body = await parse(response.body, {
headers: {
"content-type": response.headers.get("content-type")
}
})
body.json() // -> {greeting: string, file: BodyFile}
body.formData() // -> FormDataAPI
parse(source[, options]) -> {Promise<Body>}
- {AsyncIterable} source – Incoming HTTP multipart/form-data source.
-
{object} [options = {}]
- {boolean} castTypes – allow to restore type of each value (default – true)
- more information about busboy options here.
class Body
constructor(entries) -> {Body}
Create an object that allows to manipulate FormData fields taken then-busboy
Static methods
from(entries) -> {Body}
Create a new Body from given entries. An alias of new Body(entries)
-
{Array<[string[], any]>} entries – an array of Body initial path-value pairs taken from
then-busboy
json(value) -> {object}
Return an object with data taken from given entries or Body
- {Body | Array<[string[], any]>} – return an object from given Body or entries
formData(value) -> {FormData}
Return a FormData instance with data taken from given entries or Body
- {Body | Array<[string[], any]>} – return an FormData from given Body or entries
Instance properties
length -> {number}
Return an amount of entries and files in current Body instance
Instance methods
fields() -> {Body}
Return a new Body that contains fields only
files() -> {Body}
Return a new Body that contains files only
json() -> {object}
Return an object with data taken the current Body instance
formData() -> {FormData}
Return a FormData with data taken the current Body instance
entries() -> {Array<[string[], any]>}
Return an array of entries in current Body instance
values() -> {Iterator}
Return an iterator allows to go through the Body values
keys() -> {Iterator}
Return an iterator allows to go through the Body fields path
interface BodyFile
This interface reflects internal representation of a File. It is not meant to be constructed manually, but since it's compatible with files from the browsers, you can use these in Body if you need to.
Instance properties
name
Contains original name of file taken from the filename property within the form-data.
type
File MIME type
enc
Contains a value from transfer encoding header
path
Path to the file on disk
Instance methods
stream() -> {Readable}
Returns a Readable stream allowing to consume file's content
class BodyField
BodyField class in the internal representation of a regular FormData value.
constructor(value: unknown, name: string[, options]) -> {BodyField}
Creates a new instance of the BodyField class.
Instance properties
name
Returns the name of the field.
fieldnameTruncated
Indicates whether the fieldname was truncated.
valueTruncated
Indicates whether the value was truncated.
enc
Returns a value from Content-Transfer-Encoding header.
type
Returns a value from Content-Type header.
Instance methods
valueOf() -> {unknown}
Returns the value of the BodyField.
toString() -> {string}
Returns string representation of the BodyField value.
Fields format
then-busboy can restore an object structure from form-data field names if you will follow the naming formats with dots or square brackets:
Dot notation
This notation looks similarly to JS object properties accessiong syntax:
# Flat objects looks the same in both notations
# Note that the following notation examples is just a pseudo code
name = "John Doe"
age = 25
then-busboy will return the this object for an example from above:
{
name: "John Doe",
// By default, non-string values will be converted to their initial type.
// So, "25" -> 25, "null" -> null, "false" -> false etc.
age: 25
}For deep objects or collections, use dot or brackets as a separator. But don't mix them.
rootField.nestedField = "Some text here"
{
rootField: {
nestedField: "Some text here"
}
}Bracket notation
rootField[nestedField] = "I beat Twilight Sparkle and all I got was this lousy t-shirt"
Becomes
{
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"
}
]
}
}Collections allowed too:
[0][firstName] = "John"
[0][lastName] = "Doe"
[0][dob][day] = "1"
[0][dob][month] = "Jan."
[0][dob][year] = "1989"
[0][skills][0] = "Node.js"
[0][skills][1] = "CoffeeScript"
[0][skills][2] = "JavaScript"
[0][skills][3] = "Babel"
[1][firstName] = "Max"
[1][lastName] = "Doe"
[1][dob][day] = "12"
[1][dob][month] = "Mar."
[1][dob][year] = "1992"
[1][skills][0] = "Python"
[1][skills][1] = "Flask"
[1][skills][2] = "JavaScript"
[1][skills][3] = "Babel"
[1][skills][4] = "React"
[1][skills][5] = "Redux"
Then you will receive:
[
{
firstName: "John",
lastName: "Doe",
dob: {
day: 1,
month: "Jan.",
year: 1989
},
skills: ["Node.js", "CoffeeScript", "JavaScript", "Babel"]
}, {
firstName: "Max",
lastName: "Doe",
dob: {
day: 12,
month: "Mar.",
year: 1992
},
skills: ["Python", "Flask", "JavaScript", "Babel", "React", "Redux"]
}
]Limits
Whenlimits options are set, then-busboy may reject with HTTP 413 error if specified limit(s) exceeded. That will be a regular error from object http-errors package.
Related links
- formdata-node spec-compliant FormData implementation for Node.js
- @octetstream/object-to-form-data converts JavaScript object to FormData.