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# Formidable
[](https://travis-ci.org/felixge/node-formidable)
## Purpose
A Node.js module for parsing form data, especially file uploads.
## Current status
**Maintainers Wanted:** Please see https://github.com/felixge/node-formidable/issues/412
This module was developed for [Transloadit](http://transloadit.com/), a service focused on uploading
and encoding images and videos. It has been battle-tested against hundreds of GB of file uploads from
a large variety of clients and is considered production-ready.
## Features
* Fast (~500mb/sec), non-buffering multipart parser
* Automatically writing file uploads to disk
* Low memory footprint
* Graceful error handling
* Very high test coverage
## Installation
```sh
npm i -S formidable
```
This is a low-level package, and if you're using a high-level framework it may already be included. However, [Express v4](http://expressjs.com) does not include any multipart handling, nor does [body-parser](https://github.com/expressjs/body-parser).
Note: Formidable requires [gently](http://github.com/felixge/node-gently) to run the unit tests, but you won't need it for just using the library.
## Example
Parse an incoming file upload.
```javascript
var formidable = require('formidable'),
http = require('http'),
util = require('util');
http.createServer(function(req, res) {
if (req.url == '/upload' && req.method.toLowerCase() == 'post') {
// parse a file upload
var form = new formidable.IncomingForm();
form.parse(req, function(err, fields, files) {
res.writeHead(200, {'content-type': 'text/plain'});
res.write('received upload:\n\n');
res.end(util.inspect({fields: fields, files: files}));
});
return;
}
// show a file upload form
res.writeHead(200, {'content-type': 'text/html'});
res.end(
'<form action="/upload" enctype="multipart/form-data" method="post">'+
'<input type="text" name="title"><br>'+
'<input type="file" name="upload" multiple="multiple"><br>'+
'<input type="submit" value="Upload">'+
'</form>'
);
}).listen(8080);
```
## API
### Formidable.IncomingForm
```javascript
var form = new formidable.IncomingForm()
```
Creates a new incoming form.
```javascript
form.encoding = 'utf-8';
```
Sets encoding for incoming form fields.
```javascript
form.uploadDir = "/my/dir";
```
Sets the directory for placing file uploads in. You can move them later on using
`fs.rename()`. The default is `os.tmpdir()`.
```javascript
form.keepExtensions = false;
```
If you want the files written to `form.uploadDir` to include the extensions of the original files, set this property to `true`.
```javascript
form.type
```
Either 'multipart' or 'urlencoded' depending on the incoming request.
```javascript
form.maxFieldsSize = 20 * 1024 * 1024;
```
Limits the amount of memory all fields together (except files) can allocate in bytes.
If this value is exceeded, an `'error'` event is emitted. The default
size is 20MB.
```javascript
form.maxFileSize = 200 * 1024 * 1024;
```
Limits the size of uploaded file.
If this value is exceeded, an `'error'` event is emitted. The default
size is 200MB.
```javascript
form.maxFields = 1000;
```
Limits the number of fields that the querystring parser will decode. Defaults
to 1000 (0 for unlimited).
```javascript
form.hash = false;
```
If you want checksums calculated for incoming files, set this to either `'sha1'` or `'md5'`.
```javascript
form.multiples = false;
```
If this option is enabled, when you call `form.parse`, the `files` argument will contain arrays of files for inputs which submit multiple files using the HTML5 `multiple` attribute.
```javascript
form.bytesReceived
```
The amount of bytes received for this form so far.
```javascript
form.bytesExpected
```
The expected number of bytes in this form.
```javascript
form.parse(request, [cb]);
```
Parses an incoming node.js `request` containing form data. If `cb` is provided, all fields and files are collected and passed to the callback:
```javascript
form.parse(req, function(err, fields, files) {
// ...
});
form.onPart(part);
```
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.
```javascript
form.onPart = function(part) {
part.addListener('data', function() {
// ...
});
}
```
If you want to use formidable to only handle certain parts for you, you can do so:
```javascript
form.onPart = function(part) {
if (!part.filename) {
// let formidable handle all non-file parts
form.handlePart(part);
}
}
```
Check the code in this method for further inspiration.
### Formidable.File
```javascript
file.size = 0
```
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.
```javascript
file.path = null
```
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.
```javascript
file.name = null
```
The name this file had according to the uploading client.
```javascript
file.type = null
```
The mime type of this file, according to the uploading client.
```javascript
file.lastModifiedDate = 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](http://dev.w3.org/2006/webapi/FileAPI/).
```javascript
file.hash = null
```
If hash calculation was set, you can read the hex digest out of this var.
#### Formidable.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.
### Events
#### 'progress'
Emitted after each incoming chunk of data that has been parsed. Can be used to roll your own progress bar.
```javascript
form.on('progress', function(bytesReceived, bytesExpected) {
});
```
#### 'field'
Emitted whenever a field / value pair has been received.
```javascript
form.on('field', function(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.
```javascript
form.on('fileBegin', function(name, file) {
});
```
#### 'file'
Emitted whenever a field / file pair has been received. `file` is an instance of `File`.
```javascript
form.on('file', function(name, file) {
});
```
#### '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.
```javascript
form.on('error', function(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).
```javascript
form.on('aborted', function() {
});
```
##### 'end'
```javascript
form.on('end', function() {
});
```
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.
## Changelog
### v1.1.1 (2017-01-15)
* Fix DeprecationWarning about os.tmpDir() (Christian)
* Update `buffer.write` order of arguments for Node 7 (Kornel Lesiński)
* JSON Parser emits error events to the IncomingForm (alessio.montagnani)
* Improved Content-Disposition parsing (Sebastien)
* Access WriteStream of fs during runtime instead of include time (Jonas Amundsen)
* Use built-in toString to convert buffer to hex (Charmander)
* Add hash to json if present (Nick Stamas)
* Add license to package.json (Simen Bekkhus)
### v1.0.14 (2013-05-03)
* Add failing hash tests. (Ben Trask)
* Enable hash calculation again (Eugene Girshov)
* Test for immediate data events (Tim Smart)
* Re-arrange IncomingForm#parse (Tim Smart)
### v1.0.13
* Only update hash if update method exists (Sven Lito)
* According to travis v0.10 needs to go quoted (Sven Lito)
* Bumping build node versions (Sven Lito)
* Additional fix for empty requests (Eugene Girshov)
* Change the default to 1000, to match the new Node behaviour. (OrangeDog)
* Add ability to control maxKeys in the querystring parser. (OrangeDog)
* Adjust test case to work with node 0.9.x (Eugene Girshov)
* Update package.json (Sven Lito)
* Path adjustment according to eb4468b (Markus Ast)
### v1.0.12
* Emit error on aborted connections (Eugene Girshov)
* Add support for empty requests (Eugene Girshov)
* Fix name/filename handling in Content-Disposition (jesperp)
* Tolerate malformed closing boundary in multipart (Eugene Girshov)
* Ignore preamble in multipart messages (Eugene Girshov)
* Add support for application/json (Mike Frey, Carlos Rodriguez)
* Add support for Base64 encoding (Elmer Bulthuis)
* Add File#toJSON (TJ Holowaychuk)
* Remove support for Node.js 0.4 & 0.6 (Andrew Kelley)
* Documentation improvements (Sven Lito, Andre Azevedo)
* Add support for application/octet-stream (Ion Lupascu, Chris Scribner)
* Use os.tmpdir() to get tmp directory (Andrew Kelley)
* Improve package.json (Andrew Kelley, Sven Lito)
* Fix benchmark script (Andrew Kelley)
* Fix scope issue in incoming_forms (Sven Lito)
* Fix file handle leak on error (OrangeDog)
## License
Formidable is licensed under the MIT license.
## Ports
* [multipart-parser](http://github.com/FooBarWidget/multipart-parser): a C++ parser based on formidable
## Credits
* [Ryan Dahl](http://twitter.com/ryah) for his work on [http-parser](http://github.com/ry/http-parser) which heavily inspired multipart_parser.js
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