formidable [![npm version][npmv-img]][npmv-url] [![MIT license][license-img]][license-url] [![Libera Manifesto][libera-manifesto-img]][libera-manifesto-url] [![Twitter][twitter-img]][twitter-url]

> A Node.js module for parsing form data, especially file uploads.

[![Code style][codestyle-img]][codestyle-url]
[![codecoverage][codecov-img]][codecov-url]
[![linux build status][linux-build-img]][build-url]
[![windows build status][windows-build-img]][build-url]
[![macos build status][macos-build-img]][build-url]

If you have any _how-to_ kind of questions, please read the [Contributing
Guide][contributing-url] and [Code of Conduct][code_of_conduct-url]
documents.
For bugs reports and feature requests, [please create an
issue][open-issue-url] or ping @tunnckoCore
at Twitter.

[![Conventional Commits][ccommits-img]][ccommits-url]
[![Minimum Required Nodejs][nodejs-img]][npmv-url]
[![Tidelift Subcsription][tidelift-img]][tidelift-url]
[![Buy me a Kofi][kofi-img]][kofi-url]
[![Renovate App Status][renovateapp-img]][renovateapp-url]
[![Make A Pull Request][prs-welcome-img]][prs-welcome-url]

This project is semantically versioned and available as
part of the [Tidelift Subscription][tidelift-url] for professional grade
assurances, enhanced support and security.
Learn more.

_The maintainers of formidable and thousands of other packages are working
with Tidelift to deliver commercial support and maintenance for the Open Source
dependencies you use to build your applications. Save time, reduce risk, and
improve code health, while paying the maintainers of the exact dependencies you
use._

[![][npm-weekly-img]][npmv-url] [![][npm-monthly-img]][npmv-url]
[![][npm-yearly-img]][npmv-url] [![][npm-alltime-img]][npmv-url]

Status: Maintained [![npm version][npmv-canary-img]][npmv-url]

This module was initially developed by
@felixge for
Transloadit, a service focused on uploading and
encoding images and videos. It has been battle-tested against hundreds of GBs of
file uploads from a large variety of clients and is considered production-ready
and is used in production for years.

Currently, we are few maintainers trying to deal with it. :) More contributors
are always welcome! :heart: Jump on
issue #412 which is
closed, but if you are interested we can discuss it and add you after strict
rules, like enabling Two-Factor Auth in your npm and GitHub accounts.

_Note: The github master branch is a "canary" branch - try it with
npm i formidable@canary. Do not expect (for now) things from it to be inside
thelatest "dist-tag" in the Npm. Theformidable@latestis thev1.2.1 version
and probably it will be the lastv1 release!_

_Note: v2 is coming soon!_

Highlights

- Fast (~900-2500 mb/sec) & streaming multipart parser
- Automatically writing file uploads to disk (optional, see
options.fileWriteStreamHandler)
- Plugins API - allowing custom parsers and plugins
- Low memory footprint
- Graceful error handling
- Very high test coverage

Install

This project requires Node.js >= 10.13. Install it using
yarn or npm.
_We highly
recommend to use Yarn when you think to contribute to this project._

``

sh

npm install formidable

or the canary version

npm install formidable@canary





or with Yarn v1/v2

sh

yarn add formidable

or the canary version

yarn add formidable@canary





This is a low-level package, and if you're using a high-level framework it _may_

already be included. Check the examples below and the

examples/

 folder.



Examples



For more examples look at the

examples/

 directory.



$3



Parse an incoming file upload, with the

Node.js's built-in

http module

js

const http = require('http');

const formidable = require('formidable');



const server = http.createServer((req, res) => {

  if (req.url === '/api/upload' && req.method.toLowerCase() === 'post') {

    // parse a file upload

    const form = formidable({ multiples: true });



    form.parse(req, (err, fields, files) => {

      res.writeHead(200, { 'Content-Type': 'application/json' });

      res.end(JSON.stringify({ fields, files }, null, 2));

    });



    return;

  }



  // show a file upload form

  res.writeHead(200, { 'Content-Type': 'text/html' });

  res.end(

With Node.js `"http"` module

);

});



server.listen(8080, () => {

  console.log('Server listening on http://localhost:8080/ ...');

});





$3



There are multiple variants to do this, but Formidable just need Node.js Request

stream, so something like the following example should work just fine, without

any third-party Express.js middleware.



Or try the

examples/with-express.js

js

const express = require('express');

const formidable = require('formidable');



const app = express();



app.get('/', (req, res) => {

  res.send(

With `"express"` npm package

);

});



app.post('/api/upload', (req, res, next) => {

  const form = formidable({ multiples: true });



  form.parse(req, (err, fields, files) => {

    if (err) {

      next(err);

      return;

    }

    res.json({ fields, files });

  });

});



app.listen(3000, () => {

  console.log('Server listening on http://localhost:3000 ...');

});





$3



Of course, with Koa v1, v2 or future v3 the things

are very similar. You can use

formidable

 manually as shown below or through

the koa-better-body package which is

using

formidable

 under the hood and support more features and different

request bodies, check its documentation for more info.



_Note: this example is assuming Koa v2. Be aware that you should pass

ctx.req



which is Node.js's Request, and NOT the

ctx.request

 which is Koa's Request

object - there is a difference._

js

const Koa = require('koa');

const formidable = require('formidable');



const app = new Koa();



app.on('error', (err) => {

  console.error('server error', err);

});



app.use(async (ctx, next) => {

  if (ctx.url === '/api/upload' && ctx.method.toLowerCase() === 'post') {

    const form = formidable({ multiples: true });



    // not very elegant, but that's for now if you don't want to use

koa-better-body



    // or other middlewares.

    await new Promise((resolve, reject) => {

      form.parse(ctx.req, (err, fields, files) => {

        if (err) {

          reject(err);

          return;

        }



        ctx.set('Content-Type', 'application/json');

        ctx.status = 200;

        ctx.state = { fields, files };

        ctx.body = JSON.stringify(ctx.state, null, 2);

        resolve();

      });

    });

    await next();

    return;

  }



  // show a file upload form

  ctx.set('Content-Type', 'text/html');

  ctx.status = 200;

  ctx.body =

With `"koa"` npm package

;

});



app.use((ctx) => {

  console.log('The next middleware is called');

  console.log('Results:', ctx.state);

});



app.listen(3000, () => {

  console.log('Server listening on http://localhost:3000 ...');

});





Benchmarks



The benchmark is quite old, from the old codebase. But maybe quite true though.

Previously the numbers was around ~500 mb/sec. Currently with moving to the new

Node.js Streams API it's faster. You can clearly see the differences between the

Node versions.



_Note: a lot better benchmarking could and should be done in future._



Benchmarked on 8GB RAM, Xeon X3440 (2.53 GHz, 4 cores, 8 threads)



~/github/node-formidable master

❯ nve --parallel 8 10 12 13 node benchmark/bench-multipart-parser.js



 ⬢  Node 8



1261.08 mb/sec



 ⬢  Node 10



1113.04 mb/sec



 ⬢  Node 12



2107.00 mb/sec



 ⬢  Node 13



2566.42 mb/sec





!benchmark January 29th, 2020



API



$3



All shown are equivalent.



_Please pass

options

 to the function/constructor, not by assigning

them to the instance

form

js

const formidable = require('formidable');

const form = formidable(options);



// or

const { formidable } = require('formidable');

const form = formidable(options);



// or

const { IncomingForm } = require('formidable');

const form = new IncomingForm(options);



// or

const { Formidable } = require('formidable');

const form = new Formidable(options);





$3



See it's defaults in src/Formidable.js DEFAULT_OPTIONS

(the

DEFAULT_OPTIONS

 constant).



-

options.encoding {string} - default 'utf-8'

; sets encoding for

  incoming form fields,

-

options.uploadDir {string} - default os.tmpdir()

; the directory for

  placing file uploads in. You can move them later by using

fs.rename()

.

-

options.keepExtensions {boolean} - default false

; to include the

  extensions of the original files or not

-

options.allowEmptyFiles {boolean} - default true

; allow upload empty

  files

-

options.minFileSize {number} - default 1

 (1byte); the minium size of

  uploaded file.

-

options.maxFileSize {number} - default 200 1024 1024

 (200mb);

  limit the size of uploaded file.

-

options.maxFields {number} - default 1000

; limit the number of fields

  that the Querystring parser will decode, set 0 for unlimited

-

options.maxFieldsSize {number} - default 20 1024 1024

 (20mb);

  limit the amount of memory all fields together (except files) can allocate in

  bytes.

-

options.hash {string | false} - default false

; include checksums calculated

  for incoming files, set this to some hash algorithm, see

  crypto.createHash

  for available algorithms

-

options.fileWriteStreamHandler {function} - default null

, which by

  default writes to host machine file system every file parsed; The function

  should return an instance of a

  Writable stream

  that will receive the uploaded file data. With this option, you can have any

  custom behavior regarding where the uploaded file data will be streamed for.

  If you are looking to write the file uploaded in other types of cloud storages

  (AWS S3, Azure blob storage, Google cloud storage) or private file storage,

  this is the option you're looking for. When this option is defined the default

  behavior of writing the file in the host machine file system is lost.

-

options.multiples {boolean} - default false

; when you call the

.parse method, the files

 argument (of the callback) will contain arrays of

  files for inputs which submit multiple files using the HTML5

multiple



  attribute. Also, the

fields

 argument will contain arrays of values for

  fields that have names ending with '[]'.



_Note: If this size of combined fields, or size of some file is exceeded, an

'error'

 event is fired._

js

// The amount of bytes received for this form so far.

form.bytesReceived;

js

// The expected number of bytes in this form.

form.bytesExpected;





$3



Parses an incoming Node.js

request containing form data. If callback

 is

provided, all fields and files are collected and passed to the callback.

js

const formidable = require('formidable');



const form = formidable({ multiples: true, uploadDir: __dirname });



form.parse(req, (err, fields, files) => {

  console.log('fields:', fields);

  console.log('files:', files);

});





You may overwrite this method if you are interested in directly accessing the

multipart stream. Doing so will disable any

'field' / 'file'

 events

processing which would occur otherwise, making you fully responsible for

handling the processing.



About

uploadDir

, given the following directory structure



project-name

├── src

│   └── server.js

│       

└── uploads

    └── image.jpg

__dirname

 would be the same directory as the source file itself (src)

js

${__dirname}/../uploads





to put files in uploads.



Omitting

__dirname

 would make the path relative to the current working directory. This would be the same if server.js is launched from src but not project-name.

null will use default which is os.tmpdir()





Note: If the directory does not exist, the uploaded files are __silently discarded__. To make sure it exists:

js

import {createNecessaryDirectoriesSync} from "filesac";





const uploadPath =

${__dirname}/../uploads

;

createNecessaryDirectoriesSync(

${uploadPath}/x

);







In the example below, we listen on couple of events and direct them to the

data

 listener, so you can do whatever you choose there, based on whether its

before the file been emitted, the header value, the header name, on field, on

file and etc.



Or the other way could be to just override the

form.onPart

 as it's shown a bit

later.

js

form.once('error', console.error);



form.on('fileBegin', (formname, file) => {

  form.emit('data', { name: 'fileBegin', formname, value: file });

});



form.on('file', (formname, file) => {

  form.emit('data', { name: 'file', formname, value: file });

});



form.on('field', (fieldName, fieldValue) => {

  form.emit('data', { name: 'field', key: fieldName, value: fieldValue });

});



form.once('end', () => {

  console.log('Done!');

});



// If you want to customize whatever you want...

form.on('data', ({ name, key, value, buffer, start, end, formname, ...more }) => {

  if (name === 'partBegin') {

  }

  if (name === 'partData') {

  }

  if (name === 'headerField') {

  }

  if (name === 'headerValue') {

  }

  if (name === 'headerEnd') {

  }

  if (name === 'headersEnd') {

  }

  if (name === 'field') {

    console.log('field name:', key);

    console.log('field value:', value);

  }

  if (name === 'file') {

    console.log('file:', formname, value);

  }

  if (name === 'fileBegin') {

    console.log('fileBegin:', formname, value);

  }

});





$3



A method that allows you to extend the Formidable library. By default we include

4 plugins, which esentially are adapters to plug the different built-in parsers.



The plugins added by this method are always enabled.



_See src/plugins/ for more detailed look on default plugins._



The

plugin

 param has such signature:

typescript

function(formidable: Formidable, options: Options): void;





The architecture is simple. The

plugin

 is a function that is passed with the

Formidable instance (the

form

 across the README examples) and the options.



Note: the plugin function's

this

 context is also the same instance.

js

const formidable = require('formidable');



const form = formidable({ keepExtensions: true });



form.use((self, options) => {

  // self === this === form

  console.log('woohoo, custom plugin');

  // do your stuff; check

src/plugins

 for inspiration

});



form.parse(req, (error, fields, files) => {

  console.log('done!');

});





Important to note, is that inside plugin

this.options, self.options

and

options

 MAY or MAY NOT be the same. General best practice is to always use the

this

, so you can later test your plugin independently and more easily.



If you want to disable some parsing capabilities of Formidable, you can disable

the plugin which corresponds to the parser. For example, if you want to disable

multipart parsing (so the src/parsers/Multipart.js

which is used in src/plugins/multipart.js), then

you can remove it from the

options.enabledPlugins

, like so

js

const { Formidable } = require('formidable');



const form = new Formidable({

  hash: 'sha1',

  enabledPlugins: ['octetstream', 'querystring', 'json'],

});





Be aware that the order _MAY_ be important too. The names corresponds 1:1 to

files in src/plugins/ folder.



Pull requests for new built-in plugins MAY be accepted - for example, more

advanced querystring parser. Add your plugin as a new file in

src/plugins/



folder (lowercased) and follow how the other plugins are made.



$3



If you want to use Formidable to only handle certain parts for you, you can do

something similar. Or see

#387 for

inspiration, you can for example validate the mime-type.

js

const form = formidable();



form.onPart = (part) => {

  part.on('data', (buffer) => {

    // do whatever you want here

  });

};





For example, force Formidable to be used only on non-file "parts" (i.e., html

fields)

js

const form = formidable();



form.onPart = function (part) {

  // let formidable handle only non-file parts

  if (part.filename === '' || !part.mime) {

    // used internally, please do not override!

    form.handlePart(part);

  }

};

$3

ts

export interface File {

  // The size of the uploaded file in bytes.

  // If the file is still being uploaded (see

'fileBegin'

 event),

  // this property says how many bytes of the file have been written to disk yet.

  file.size: number;



  // The path this file is being written to. You can modify this in the

'fileBegin'

 event in

  // case you are unhappy with the way formidable generates a temporary path for your files.

  file.path: string;



  // The name this file had according to the uploading client.

  file.name: string | null;



  // The mime type of this file, according to the uploading client.

  file.type: string | null;



  // A Date object (or

null

) containing the time this file was last written to.

  // Mostly here for compatibility with the W3C File API Draft.

  file.lastModifiedDate: Date | null;



  // If

options.hash

 calculation was set, you can read the hex digest out of this var.

  file.hash: string | 'sha1' | 'md5' | 'sha256' | null;

}





#### file.toJSON()



This method returns a JSON-representation of the file, allowing you to

JSON.stringify()

 the file which is useful for logging and responding to

requests.



$3



####

'progress'





Emitted after each incoming chunk of data that has been parsed. Can be used to

roll your own progress bar.

js

form.on('progress', (bytesReceived, bytesExpected) => {});





####

'field'





Emitted whenever a field / value pair has been received.

js

form.on('field', (name, value) => {});





####

'fileBegin'





Emitted whenever a new file is detected in the upload stream. Use this event if

you want to stream the file to somewhere else while buffering the upload on the

file system.

js

form.on('fileBegin', (formName, file) => {

    // accessible here 

    // formName the name in the form ()

    // file.name (http filename)

    // file.path default pathnme as per options.uploadDir and options.filename

    // file.path = CUSTOM_PATH // to change the final path

});





####

'file'





Emitted whenever a field / file pair has been received.

file

 is an instance of

File

js

form.on('file', (formname, file) => {

    // same as fileBegin, except

    // it is too late to change file.path

    // file.hash is available if options.hash was used

});





####

'error'





Emitted when there is an error processing the incoming form. A request that

experiences an error is automatically paused, you will have to manually call

request.resume() if you want the request to continue firing 'data'

 events.

js

form.on('error', (err) => {});





####

'aborted'





Emitted when the request was aborted by the user. Right now this can be due to a

'timeout' or 'close' event on the socket. After this event is emitted, an

error

 event will follow. In the future there will be a separate 'timeout'

event (needs a change in the node core).

js

form.on('aborted', () => {});





####

'end'





Emitted when the entire request has been received, and all contained files have

finished flushing to disk. This is a great place for you to send your response.

js

form.on('end', () => {});





Ports & Credits



- multipart-parser: a C++

  parser based on formidable

- Ryan Dahl for his work on

  http-parser which heavily inspired the

  initial

multipart_parser.js

.



Contributing



If the documentation is unclear or has a typo, please click on the page's

Edit`
button (pencil icon) and suggest a correction. If you would like to help us fix
a bug or add a new feature, please check our [Contributing
Guide][contributing-url]. Pull requests are welcome!

Thanks goes to these wonderful people
(emoji key):

_{Felix Geisendörfer} 💻 🎨 🤔 📖	_{Charlike Mike Reagent} 🐛 🚇 🎨 💻 📖 💡 🤔 🚧 ⚠️	_Kedar 💻 ⚠️ 💬 🐛	_{Walle Cyril} 💬 🐛 💻 💵 🤔 🚧	_Xargs 💬 🐛 💻 🚧	_Amit-A 💬 🐛 💻
_Charmander 💬 🐛 💻 🤔 🚧	_{Dylan Piercey} 🤔	_{Adam Dobrawy} 🐛 📖	_amitrohatgi 🤔	_{Jesse Feng} 🐛	_{Nathanael Demacon} 💬 💻 👀
_MunMunMiao 🐛	_{Gabriel Petrovay} 🐛 💻	_{Philip Woods} 💻 🤔	_{Dmitry Ivonin} 📖	_{Claudio Poli} 💻

From a Felix blog post:

- Sven Lito for fixing bugs and merging patches
- egirshov for contributing many improvements to the node-formidable multipart parser
- Andrew Kelley for also helping with fixing bugs and making improvements
- Mike Frey for contributing JSON support

License

Formidable is licensed under the [MIT License][license-url].

[codestyle-url]: https://github.com/airbnb/javascript
[codestyle-img]: https://badgen.net/badge/code%20style/airbnb%20%2B%20prettier/ff5a5f?icon=airbnb&cache=300
[codecov-url]: https://codecov.io/gh/node-formidable/formidable
[codecov-img]: https://badgen.net/codecov/c/github/node-formidable/formidable/master?icon=codecov
[npmv-canary-img]: https://badgen.net/npm/v/formidable/canary?icon=npm
[npmv-dev-img]: https://badgen.net/npm/v/formidable/dev?icon=npm
[npmv-img]: https://badgen.net/npm/v/formidable?icon=npm
[npmv-url]: https://npmjs.com/package/formidable
[license-img]: https://badgen.net/npm/license/formidable
[license-url]: https://github.com/node-formidable/formidable/blob/master/LICENSE
[chat-img]: https://badgen.net/badge/chat/on%20gitter/46BC99?icon=gitter
[chat-url]: https://gitter.im/node-formidable/Lobby
[libera-manifesto-url]: https://liberamanifesto.com
[libera-manifesto-img]: https://badgen.net/badge/libera/manifesto/grey
[renovateapp-url]: https://renovatebot.com
[renovateapp-img]: https://badgen.net/badge/renovate/enabled/green?cache=300
[prs-welcome-img]: https://badgen.net/badge/PRs/welcome/green?cache=300
[prs-welcome-url]: http://makeapullrequest.com
[twitter-url]: https://twitter.com/tunnckoCore
[twitter-img]: https://badgen.net/twitter/follow/tunnckoCore?icon=twitter&color=1da1f2&cache=300

[npm-weekly-img]: https://badgen.net/npm/dw/formidable?icon=npm&cache=300
[npm-monthly-img]: https://badgen.net/npm/dm/formidable?icon=npm&cache=300
[npm-yearly-img]: https://badgen.net/npm/dy/formidable?icon=npm&cache=300
[npm-alltime-img]: https://badgen.net/npm/dt/formidable?icon=npm&cache=300&label=total%20downloads

[nodejs-img]: https://badgen.net/badge/node/>=%2010.13/green?cache=300

[ccommits-url]: https://conventionalcommits.org/
[ccommits-img]: https://badgen.net/badge/conventional%20commits/v1.0.0/green?cache=300

[contributing-url]: https://github.com/node-formidable/.github/blob/master/CONTRIBUTING.md
[code_of_conduct-url]: https://github.com/node-formidable/.github/blob/master/CODE_OF_CONDUCT.md

[open-issue-url]: https://github.com/node-formidable/formidable/issues/new

[tidelift-url]: https://tidelift.com/subscription/pkg/npm-formidable?utm_source=npm-formidable&utm_medium=referral&utm_campaign=enterprise
[tidelift-img]: https://badgen.net/badge/tidelift/subscription/4B5168?labelColor=F6914D

[kofi-url]: https://ko-fi.com/tunnckoCore/commissions
[kofi-img]: https://badgen.net/badge/ko-fi/support/29abe0c2?cache=300&icon=https://rawcdn.githack.com/tunnckoCore/badgen-icons/f8264c6414e0bec449dd86f2241d50a9b89a1203/icons/kofi.svg

[linux-build-img]: https://badgen-net.charlike.now.sh/github/checks/node-formidable/formidable/master/ubuntu?cache=300&label=linux%20build&icon=github
[macos-build-img]: https://badgen-net.charlike.now.sh/github/checks/node-formidable/formidable/master/macos?cache=300&label=macos%20build&icon=github
[windows-build-img]: https://badgen-net.charlike.now.sh/github/checks/node-formidable/formidable/master/windows?cache=300&label=windows%20build&icon=github
[build-url]: https://github.com/node-formidable/formidable/actions?query=workflow%3Anodejs

formidable [![npm version][npmv-img]][npmv-url] [![MIT license][license-img]][license-url] [![Libera Manifesto][libera-manifesto-img]][libera-manifesto-url] [![Twitter][twitter-img]][twitter-url]

Status: Maintained [![npm version][npmv-canary-img]][npmv-url]

Highlights

Install

This project requires Node.js >= 10.13. Install it using
yarn or npm.
_We highly
recommend to use Yarn when you think to contribute to this project._

``

sh

npm install formidable

or the canary version

npm install formidable@canary





or with Yarn v1/v2

sh

yarn add formidable

or the canary version

yarn add formidable@canary





This is a low-level package, and if you're using a high-level framework it _may_

already be included. Check the examples below and the

examples/

 folder.



Examples



For more examples look at the

examples/

 directory.



$3



Parse an incoming file upload, with the

Node.js's built-in

http module

js

const http = require('http');

const formidable = require('formidable');



const server = http.createServer((req, res) => {

  if (req.url === '/api/upload' && req.method.toLowerCase() === 'post') {

    // parse a file upload

    const form = formidable({ multiples: true });



    form.parse(req, (err, fields, files) => {

      res.writeHead(200, { 'Content-Type': 'application/json' });

      res.end(JSON.stringify({ fields, files }, null, 2));

    });



    return;

  }



  // show a file upload form

  res.writeHead(200, { 'Content-Type': 'text/html' });

  res.end(

With Node.js `"http"` module

);

});



server.listen(8080, () => {

  console.log('Server listening on http://localhost:8080/ ...');

});





$3



There are multiple variants to do this, but Formidable just need Node.js Request

stream, so something like the following example should work just fine, without

any third-party Express.js middleware.



Or try the

examples/with-express.js

js

const express = require('express');

const formidable = require('formidable');



const app = express();



app.get('/', (req, res) => {

  res.send(

With `"express"` npm package

);

});



app.post('/api/upload', (req, res, next) => {

  const form = formidable({ multiples: true });



  form.parse(req, (err, fields, files) => {

    if (err) {

      next(err);

      return;

    }

    res.json({ fields, files });

  });

});



app.listen(3000, () => {

  console.log('Server listening on http://localhost:3000 ...');

});





$3



Of course, with Koa v1, v2 or future v3 the things

are very similar. You can use

formidable

 manually as shown below or through

the koa-better-body package which is

using

formidable

 under the hood and support more features and different

request bodies, check its documentation for more info.



_Note: this example is assuming Koa v2. Be aware that you should pass

ctx.req



which is Node.js's Request, and NOT the

ctx.request

 which is Koa's Request

object - there is a difference._

js

const Koa = require('koa');

const formidable = require('formidable');



const app = new Koa();



app.on('error', (err) => {

  console.error('server error', err);

});



app.use(async (ctx, next) => {

  if (ctx.url === '/api/upload' && ctx.method.toLowerCase() === 'post') {

    const form = formidable({ multiples: true });



    // not very elegant, but that's for now if you don't want to use

koa-better-body



    // or other middlewares.

    await new Promise((resolve, reject) => {

      form.parse(ctx.req, (err, fields, files) => {

        if (err) {

          reject(err);

          return;

        }



        ctx.set('Content-Type', 'application/json');

        ctx.status = 200;

        ctx.state = { fields, files };

        ctx.body = JSON.stringify(ctx.state, null, 2);

        resolve();

      });

    });

    await next();

    return;

  }



  // show a file upload form

  ctx.set('Content-Type', 'text/html');

  ctx.status = 200;

  ctx.body =

With `"koa"` npm package

;

});



app.use((ctx) => {

  console.log('The next middleware is called');

  console.log('Results:', ctx.state);

});



app.listen(3000, () => {

  console.log('Server listening on http://localhost:3000 ...');

});





Benchmarks



The benchmark is quite old, from the old codebase. But maybe quite true though.

Previously the numbers was around ~500 mb/sec. Currently with moving to the new

Node.js Streams API it's faster. You can clearly see the differences between the

Node versions.



_Note: a lot better benchmarking could and should be done in future._



Benchmarked on 8GB RAM, Xeon X3440 (2.53 GHz, 4 cores, 8 threads)



~/github/node-formidable master

❯ nve --parallel 8 10 12 13 node benchmark/bench-multipart-parser.js



 ⬢  Node 8



1261.08 mb/sec



 ⬢  Node 10



1113.04 mb/sec



 ⬢  Node 12



2107.00 mb/sec



 ⬢  Node 13



2566.42 mb/sec





!benchmark January 29th, 2020



API



$3



All shown are equivalent.



_Please pass

options

 to the function/constructor, not by assigning

them to the instance

form

js

const formidable = require('formidable');

const form = formidable(options);



// or

const { formidable } = require('formidable');

const form = formidable(options);



// or

const { IncomingForm } = require('formidable');

const form = new IncomingForm(options);



// or

const { Formidable } = require('formidable');

const form = new Formidable(options);





$3



See it's defaults in src/Formidable.js DEFAULT_OPTIONS

(the

DEFAULT_OPTIONS

 constant).



-

options.encoding {string} - default 'utf-8'

; sets encoding for

  incoming form fields,

-

options.uploadDir {string} - default os.tmpdir()

; the directory for

  placing file uploads in. You can move them later by using

fs.rename()

.

-

options.keepExtensions {boolean} - default false

; to include the

  extensions of the original files or not

-

options.allowEmptyFiles {boolean} - default true

; allow upload empty

  files

-

options.minFileSize {number} - default 1

 (1byte); the minium size of

  uploaded file.

-

options.maxFileSize {number} - default 200 1024 1024

 (200mb);

  limit the size of uploaded file.

-

options.maxFields {number} - default 1000

; limit the number of fields

  that the Querystring parser will decode, set 0 for unlimited

-

options.maxFieldsSize {number} - default 20 1024 1024

 (20mb);

  limit the amount of memory all fields together (except files) can allocate in

  bytes.

-

options.hash {string | false} - default false

; include checksums calculated

  for incoming files, set this to some hash algorithm, see

  crypto.createHash

  for available algorithms

-

options.fileWriteStreamHandler {function} - default null

, which by

  default writes to host machine file system every file parsed; The function

  should return an instance of a

  Writable stream

  that will receive the uploaded file data. With this option, you can have any

  custom behavior regarding where the uploaded file data will be streamed for.

  If you are looking to write the file uploaded in other types of cloud storages

  (AWS S3, Azure blob storage, Google cloud storage) or private file storage,

  this is the option you're looking for. When this option is defined the default

  behavior of writing the file in the host machine file system is lost.

-

options.multiples {boolean} - default false

; when you call the

.parse method, the files

 argument (of the callback) will contain arrays of

  files for inputs which submit multiple files using the HTML5

multiple



  attribute. Also, the

fields

 argument will contain arrays of values for

  fields that have names ending with '[]'.



_Note: If this size of combined fields, or size of some file is exceeded, an

'error'

 event is fired._

js

// The amount of bytes received for this form so far.

form.bytesReceived;

js

// The expected number of bytes in this form.

form.bytesExpected;





$3



Parses an incoming Node.js

request containing form data. If callback

 is

provided, all fields and files are collected and passed to the callback.

js

const formidable = require('formidable');



const form = formidable({ multiples: true, uploadDir: __dirname });



form.parse(req, (err, fields, files) => {

  console.log('fields:', fields);

  console.log('files:', files);

});





You may overwrite this method if you are interested in directly accessing the

multipart stream. Doing so will disable any

'field' / 'file'

 events

processing which would occur otherwise, making you fully responsible for

handling the processing.



About

uploadDir

, given the following directory structure



project-name

├── src

│   └── server.js

│       

└── uploads

    └── image.jpg

__dirname

 would be the same directory as the source file itself (src)

js

${__dirname}/../uploads





to put files in uploads.



Omitting

__dirname

 would make the path relative to the current working directory. This would be the same if server.js is launched from src but not project-name.

null will use default which is os.tmpdir()





Note: If the directory does not exist, the uploaded files are __silently discarded__. To make sure it exists:

js

import {createNecessaryDirectoriesSync} from "filesac";





const uploadPath =

${__dirname}/../uploads

;

createNecessaryDirectoriesSync(

${uploadPath}/x

);







In the example below, we listen on couple of events and direct them to the

data

 listener, so you can do whatever you choose there, based on whether its

before the file been emitted, the header value, the header name, on field, on

file and etc.



Or the other way could be to just override the

form.onPart

 as it's shown a bit

later.

js

form.once('error', console.error);



form.on('fileBegin', (formname, file) => {

  form.emit('data', { name: 'fileBegin', formname, value: file });

});



form.on('file', (formname, file) => {

  form.emit('data', { name: 'file', formname, value: file });

});



form.on('field', (fieldName, fieldValue) => {

  form.emit('data', { name: 'field', key: fieldName, value: fieldValue });

});



form.once('end', () => {

  console.log('Done!');

});



// If you want to customize whatever you want...

form.on('data', ({ name, key, value, buffer, start, end, formname, ...more }) => {

  if (name === 'partBegin') {

  }

  if (name === 'partData') {

  }

  if (name === 'headerField') {

  }

  if (name === 'headerValue') {

  }

  if (name === 'headerEnd') {

  }

  if (name === 'headersEnd') {

  }

  if (name === 'field') {

    console.log('field name:', key);

    console.log('field value:', value);

  }

  if (name === 'file') {

    console.log('file:', formname, value);

  }

  if (name === 'fileBegin') {

    console.log('fileBegin:', formname, value);

  }

});





$3



A method that allows you to extend the Formidable library. By default we include

4 plugins, which esentially are adapters to plug the different built-in parsers.



The plugins added by this method are always enabled.



_See src/plugins/ for more detailed look on default plugins._



The

plugin

 param has such signature:

typescript

function(formidable: Formidable, options: Options): void;





The architecture is simple. The

plugin

 is a function that is passed with the

Formidable instance (the

form

 across the README examples) and the options.



Note: the plugin function's

this

 context is also the same instance.

js

const formidable = require('formidable');



const form = formidable({ keepExtensions: true });



form.use((self, options) => {

  // self === this === form

  console.log('woohoo, custom plugin');

  // do your stuff; check

src/plugins

 for inspiration

});



form.parse(req, (error, fields, files) => {

  console.log('done!');

});





Important to note, is that inside plugin

this.options, self.options

and

options

 MAY or MAY NOT be the same. General best practice is to always use the

this

, so you can later test your plugin independently and more easily.



If you want to disable some parsing capabilities of Formidable, you can disable

the plugin which corresponds to the parser. For example, if you want to disable

multipart parsing (so the src/parsers/Multipart.js

which is used in src/plugins/multipart.js), then

you can remove it from the

options.enabledPlugins

, like so

js

const { Formidable } = require('formidable');



const form = new Formidable({

  hash: 'sha1',

  enabledPlugins: ['octetstream', 'querystring', 'json'],

});





Be aware that the order _MAY_ be important too. The names corresponds 1:1 to

files in src/plugins/ folder.



Pull requests for new built-in plugins MAY be accepted - for example, more

advanced querystring parser. Add your plugin as a new file in

src/plugins/



folder (lowercased) and follow how the other plugins are made.



$3



If you want to use Formidable to only handle certain parts for you, you can do

something similar. Or see

#387 for

inspiration, you can for example validate the mime-type.

js

const form = formidable();



form.onPart = (part) => {

  part.on('data', (buffer) => {

    // do whatever you want here

  });

};





For example, force Formidable to be used only on non-file "parts" (i.e., html

fields)

js

const form = formidable();



form.onPart = function (part) {

  // let formidable handle only non-file parts

  if (part.filename === '' || !part.mime) {

    // used internally, please do not override!

    form.handlePart(part);

  }

};

$3

ts

export interface File {

  // The size of the uploaded file in bytes.

  // If the file is still being uploaded (see

'fileBegin'

 event),

  // this property says how many bytes of the file have been written to disk yet.

  file.size: number;



  // The path this file is being written to. You can modify this in the

'fileBegin'

 event in

  // case you are unhappy with the way formidable generates a temporary path for your files.

  file.path: string;



  // The name this file had according to the uploading client.

  file.name: string | null;



  // The mime type of this file, according to the uploading client.

  file.type: string | null;



  // A Date object (or

null

) containing the time this file was last written to.

  // Mostly here for compatibility with the W3C File API Draft.

  file.lastModifiedDate: Date | null;



  // If

options.hash

 calculation was set, you can read the hex digest out of this var.

  file.hash: string | 'sha1' | 'md5' | 'sha256' | null;

}





#### file.toJSON()



This method returns a JSON-representation of the file, allowing you to

JSON.stringify()

 the file which is useful for logging and responding to

requests.



$3



####

'progress'





Emitted after each incoming chunk of data that has been parsed. Can be used to

roll your own progress bar.

js

form.on('progress', (bytesReceived, bytesExpected) => {});





####

'field'





Emitted whenever a field / value pair has been received.

js

form.on('field', (name, value) => {});





####

'fileBegin'





Emitted whenever a new file is detected in the upload stream. Use this event if

you want to stream the file to somewhere else while buffering the upload on the

file system.

js

form.on('fileBegin', (formName, file) => {

    // accessible here 

    // formName the name in the form ()

    // file.name (http filename)

    // file.path default pathnme as per options.uploadDir and options.filename

    // file.path = CUSTOM_PATH // to change the final path

});





####

'file'





Emitted whenever a field / file pair has been received.

file

 is an instance of

File

js

form.on('file', (formname, file) => {

    // same as fileBegin, except

    // it is too late to change file.path

    // file.hash is available if options.hash was used

});





####

'error'





Emitted when there is an error processing the incoming form. A request that

experiences an error is automatically paused, you will have to manually call

request.resume() if you want the request to continue firing 'data'

 events.

js

form.on('error', (err) => {});





####

'aborted'





Emitted when the request was aborted by the user. Right now this can be due to a

'timeout' or 'close' event on the socket. After this event is emitted, an

error

 event will follow. In the future there will be a separate 'timeout'

event (needs a change in the node core).

js

form.on('aborted', () => {});





####

'end'





Emitted when the entire request has been received, and all contained files have

finished flushing to disk. This is a great place for you to send your response.

js

form.on('end', () => {});





Ports & Credits



- multipart-parser: a C++

  parser based on formidable

- Ryan Dahl for his work on

  http-parser which heavily inspired the

  initial

multipart_parser.js

.



Contributing



If the documentation is unclear or has a typo, please click on the page's

_{Felix Geisendörfer} 💻 🎨 🤔 📖	_{Charlike Mike Reagent} 🐛 🚇 🎨 💻 📖 💡 🤔 🚧 ⚠️	_Kedar 💻 ⚠️ 💬 🐛	_{Walle Cyril} 💬 🐛 💻 💵 🤔 🚧	_Xargs 💬 🐛 💻 🚧	_Amit-A 💬 🐛 💻
_Charmander 💬 🐛 💻 🤔 🚧	_{Dylan Piercey} 🤔	_{Adam Dobrawy} 🐛 📖	_amitrohatgi 🤔	_{Jesse Feng} 🐛	_{Nathanael Demacon} 💬 💻 👀
_MunMunMiao 🐛	_{Gabriel Petrovay} 🐛 💻	_{Philip Woods} 💻 🤔	_{Dmitry Ivonin} 📖	_{Claudio Poli} 💻

@grimmopher/formidable

formidable [![npm version][npmv-img]][npmv-url] [![MIT license][license-img]][license-url] [![Libera Manifesto][libera-manifesto-img]][libera-manifesto-url] [![Twitter][twitter-img]][twitter-url]

Status: Maintained [![npm version][npmv-canary-img]][npmv-url]

Highlights

Install

or the canary version

or the canary version

Examples

$3

With Node.js "http" module

$3

With "express" npm package

$3

With "koa" npm package

Benchmarks

API

$3

$3

$3

$3

$3

$3

$3

Ports & Credits

Contributing

License

@grimmopher/formidable

formidable [![npm version][npmv-img]][npmv-url] [![MIT license][license-img]][license-url] [![Libera Manifesto][libera-manifesto-img]][libera-manifesto-url] [![Twitter][twitter-img]][twitter-url]

Status: Maintained [![npm version][npmv-canary-img]][npmv-url]

Highlights

Install

or the canary version

or the canary version

Examples

$3

With Node.js "http" module

$3

With "express" npm package

$3

With "koa" npm package

Benchmarks

API

$3

$3

$3

$3

$3

$3

$3

Ports & Credits

Contributing

License

Dist Tags

With Node.js `"http"` module

With `"express"` npm package

With `"koa"` npm package

With Node.js `"http"` module

With `"express"` npm package

With `"koa"` npm package