FormData

FormData implementation for Node.js. Built over Readable stream and async generators. Can be used to communicate between servers with multipart/form-data format.

Installation

You can install this package from npm:

npm install formdata-node

Or with yarn:

yarn add formdata-node

Usage

Each FormData instance allows you to read its data from Readable stream, just use FormData#stream property for that.

You can send queries via HTTP clients that supports headers setting Readable stream as body.

Let's take a look at minimal example with got:

import FormData from "formdata-node"
import got from "got"

const fd = new FormData()

fd.set("greeting", "Hello, World!")

const options = {
  body: fd.stream, // Set internal stream as request body
  headers: fd.headers // Set headers of the current FormData instance
}

got.post("http://example.com", options)
  .then(res => console.log("Res: ", res.body))
  .catch(err => console.error("Error: ", err))

API

constructor FormData([fields])

Initialize new FormData instance

• {array} [fields = null] – an optional FormData initial fields. Each initial field should be passed as an array with 3 elemtnts as a collection of the objects with "name", "value" and "filename" props. See the FormData#append for more info about the available format.

Instance properties

get boundary() -> {string}

Returns a boundary string of the current FormData instance.

get stream() -> {stream.Readable}

Returns an internal Readable stream. Use it to send queries, but don't push anything into it.

get headers() -> {object}

Returns object with content-type header

Instance methods

set(name, value[, filename]) -> {void}

Set a new value for an existing key inside FormData, or add the new field if it does not already exist.

• {string} name – The name of the field whose data is contained in value
• {any} value – The field value. You can pass any JavaScript primitive type (including null and undefined), Buffer or Readable stream. Note that Arrays and Object will be converted to string by using String function.
• {string} [filename = undefined] – A filename of given field. Can be added only for Buffer and Readable .

append(name, value[, filename]) -> {void}

Appends a new value onto an existing key inside a FormData object, or adds the key if it does not already exist.

• {string} name – The name of the field whose data is contained in value
• {any} value – The field value. You can pass any JavaScript primitive type (including null and undefined), Buffer or Readable stream. Note that Arrays and Object will be converted to string by using String function.
• {string} [filename = undefined] – A filename of given field. Can be added only for Buffer and Readable .

get(name) -> {string | Buffer | stream.Readable | fs.ReadStream}

Returns the first value associated with the given name. Buffer and Readable values will be returned as-is.

• {string} name – A name of the value you want to retrieve.

getAll(name) -> {Array<string | Buffer | stream.Readable | fs.ReadStream>}

Returns all the values associated with a given key from within a FormData object.

• {string} name – A name of the value you want to retrieve.

has(name) -> {boolean}

Check if a field with the given name exists inside FormData.

• {string} – A name of the field you want to test for.

delete(name) -> {void}

Deletes a key and its value(s) from a FormData object.

• {string} name – The name of the key you want to delete.

getComputedLength() -> {Promise<number>}

Returns computed length of the FormData content. If FormData instance contains a field with stream.Readable value, this method will always return undefined.

forEach(callback[, ctx]) -> {void}

Executes a given callback for each field of the FormData instance

• {function} callback – Function to execute for each element, taking three arguments:
  • {any} value – A value(s) of the current field.
  • {string} name – Name of the current field.
  • {FormData} fd – The FormData instance that forEach is being applied to
• {any} [ctx = null] – Value to use as this context when executing the given callback

keys() -> {IterableIterator<string>}

Returns an iterator allowing to go through the FormData keys

values() -> {IterableIterator<any>}

Returns an iterator allowing to go through the FormData values

entries() -> {IterableIterator<[string, any]>}

Returns an iterator allowing to go through the FormData key/value pairs

[Symbol.iterator]() -> {IterableIterator<[string, any]>}

An alias of FormData#entries

[Symbol.asyncIterator]() -> {IterableIterator<Promise<Buffer>>}

Returns an async iterator allowing to read a data from internal Readable stream using for-await syntax. Read the async iteration proposal to get more info about async iterators.

Related links

• then-busboy is a promise-based wrapper around Busboy. Process multipart/form-data content and returns it as a single object. Will be helpful to handle your data on the server-side applications.
• @octetstream/object-to-form-data converts JavaScript object to FormData.
• FormData interface documentation on MDN