multiparty

Parse http requests with content-type multipart/form-data, also known as file uploads.

See also busboy - a
faster alternative
which may be worth looking into.

Installation

This is a Node.js module available through the
npm registry. Installation is done using the
npm install command:

npm install multiparty

Usage

• See examples.

Parse an incoming multipart/form-data request.

 var multiparty = require('multiparty');
var http = require('http');
var util = require('util');

http.createServer(function(req, res) {
  if (req.url === '/upload' && req.method === 'POST') {
    // parse a file upload
    var form = new multiparty.Form();

    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

multiparty.Form

 var form = new multiparty.Form(options)

Creates a new form. Options:

• encoding - sets encoding for the incoming form fields. Defaults to utf8.
• maxFieldsSize - Limits the amount of memory all fields (not files) can
  allocate in bytes. If this value is exceeded, an error event is emitted.
  The default size is 2MB.
• maxFields - Limits the number of fields that will be parsed before
  emitting an error event. A file counts as a field in this case.
  Defaults to 1000.
• maxFilesSize - Only relevant when autoFiles is true. Limits the
  total bytes accepted for all files combined. If this value is exceeded,
  an error event is emitted. The default is Infinity.
• autoFields - Enables field events and disables part events for fields.
  This is automatically set to true if you add a field listener.
• autoFiles - Enables file events and disables part events for files.
  This is automatically set to true if you add a file listener.
• uploadDir - Only relevant when autoFiles is true. The directory for
  placing file uploads in. You can move them later using fs.rename().
  Defaults to os.tmpdir().

form.parse(request, [cb])

Parses an incoming node.js request containing form data.This will cause
form to emit events based off the incoming request.

 var count = 0;
var form = new multiparty.Form();

// Errors may be emitted
// Note that if you are listening to 'part' events, the same error may be
// emitted from the `form` and the `part`.
form.on('error', function(err) {
  console.log('Error parsing form: ' + err.stack);
});

// Parts are emitted when parsing the form
form.on('part', function(part) {
  // You *must* act on the part by reading it
  // NOTE: if you want to ignore it, just call "part.resume()"

  if (part.filename === undefined) {
    // filename is not defined when this is a field and not a file
    console.log('got field named ' + part.name);
    // ignore field's content
    part.resume();
  }

  if (part.filename !== undefined) {
    // filename is defined when this is a file
    count++;
    console.log('got file named ' + part.name);
    // ignore file's content here
    part.resume();
  }

  part.on('error', function(err) {
    // decide what to do
  });
});

// Close emitted after form parsed
form.on('close', function() {
  console.log('Upload completed!');
  res.setHeader('text/plain');
  res.end('Received ' + count + ' files');
});

// Parse req
form.parse(req);

If cb is provided, autoFields and autoFiles are set to true and all
fields and files are collected and passed to the callback, removing the need to
listen to any events on form. This is for convenience when you want to read
everything, but be sure to write cleanup code, as this will write all uploaded
files to the disk, even ones you may not be interested in.

 form.parse(req, function(err, fields, files) {
  Object.keys(fields).forEach(function(name) {
    console.log('got field named ' + name);
  });

  Object.keys(files).forEach(function(name) {
    console.log('got file named ' + name);
  });

  console.log('Upload completed!');
  res.setHeader('text/plain');
  res.end('Received ' + files.length + ' files');
});

fields is an object where the property names are field names and the values
are arrays of field values.

files is an object where the property names are field names and the values
are arrays of file objects.

form.bytesReceived

The amount of bytes received for this form so far.

form.bytesExpected

The expected number of bytes in this form.

Events

'error' (err)

Unless you supply a callback to form.parse, you definitely want to handle
this event. Otherwise your server will crash when users submit bogus
multipart requests!

Only one 'error' event can ever be emitted, and if an 'error' event is
emitted, then 'close' will not be emitted.

If the error would correspond to a certain HTTP response code, the err object
will have a statusCode property with the value of the suggested HTTP response
code to send back.

Note that an 'error' event will be emitted both from the form and from the
current part.

'part' (part)

Emitted when a part is encountered in the request. part is a
ReadableStream. It also has the following properties:

• headers - the headers for this part. For example, you may be interested
  in content-type.
• name - the field name for this part
• filename - only if the part is an incoming file
• byteOffset - the byte offset of this part in the request body
• byteCount - assuming that this is the last part in the request,
  this is the size of this part in bytes. You could use this, for
  example, to set the Content-Length header if uploading to S3.
  If the part had a Content-Length header then that value is used
  here instead.

Parts for fields are not emitted when autoFields is on, and likewise parts
for files are not emitted when autoFiles is on.

part emits 'error' events! Make sure you handle them.

'aborted'

Emitted when the request is aborted. This event will be followed shortly
by an error event. In practice you do not need to handle this event.

'progress' (bytesReceived, bytesExpected)

Emitted when a chunk of data is received for the form. The bytesReceived
argument contains the total count of bytes received for this form so far. The
bytesExpected argument contains the total expected bytes if known, otherwise
null.

'close'

Emitted after all parts have been parsed and emitted. Not emitted if an error
event is emitted.

If you have autoFiles on, this is not fired until all the data has been
flushed to disk and the file handles have been closed.

This is typically when you would send your response.

'file' (name, file)

By default multiparty will not touch your hard drive. But if you add this
listener, multiparty automatically sets form.autoFiles to true and will
stream uploads to disk for you.

The max bytes accepted per request can be specified with maxFilesSize.

• name - the field name for this file
• file - an object with these properties:
  • fieldName - same as name - the field name for this file
  • originalFilename - the filename that the user reports for the file
  • path - the absolute path of the uploaded file on disk
  • headers - the HTTP headers that were sent along with this file
  • size - size of the file in bytes

'field' (name, value)

• name - field name
• value - string field value

License

MIT