formidable
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The formidable npm package is a Node.js module for parsing form data, especially file uploads. It can handle multipart/form-data, which is used for uploading files through forms.
File Upload
This code creates an HTTP server that listens for POST requests on the '/upload' path. It uses formidable to parse the incoming form data and handle file uploads.
const formidable = require('formidable');
const http = require('http');
http.createServer((req, res) => {
if (req.url === '/upload' && req.method.toLowerCase() === 'post') {
const form = new formidable.IncomingForm();
form.parse(req, (err, fields, files) => {
if (err) {
res.writeHead(500, { 'content-type': 'text/plain' });
res.end('Error parsing the files');
return;
}
res.writeHead(200, { 'content-type': 'text/plain' });
res.write('Files uploaded successfully:\n');
res.end(JSON.stringify(files, null, 2));
});
}
}).listen(8080);Form Field Parsing
This code snippet demonstrates how to use formidable to parse regular form fields (text inputs, selects, etc.) in addition to file uploads.
const formidable = require('formidable');
const http = require('http');
http.createServer((req, res) => {
if (req.url === '/submit' && req.method.toLowerCase() === 'post') {
const form = new formidable.IncomingForm();
form.parse(req, (err, fields, files) => {
if (err) {
res.writeHead(500, { 'content-type': 'text/plain' });
res.end('Error parsing the form fields');
return;
}
res.writeHead(200, { 'content-type': 'text/plain' });
res.write('Form fields submitted:\n');
res.end(JSON.stringify(fields, null, 2));
});
}
}).listen(8080);File Upload Progress
This example shows how to track the progress of a file upload using formidable's 'progress' event, which provides the bytes received and the total bytes expected.
const formidable = require('formidable');
const http = require('http');
http.createServer((req, res) => {
if (req.url === '/upload' && req.method.toLowerCase() === 'post') {
const form = new formidable.IncomingForm();
form.on('progress', (bytesReceived, bytesExpected) => {
console.log(`Progress: ${bytesReceived}/${bytesExpected}`);
});
form.parse(req, (err, fields, files) => {
// Handle file upload and response
});
}
}).listen(8080);Multer is another popular Node.js middleware for handling multipart/form-data, which is primarily used for uploading files. It is built on top of busboy for maximum efficiency. Unlike formidable, multer is specifically designed for use with Express applications and includes more options for file storage and manipulation.
Busboy is a low-level Node.js module for parsing multipart/form-data request bodies. Formidable is actually built on top of busboy. Busboy is faster and more efficient but requires more setup and manual handling compared to formidable, which provides a higher-level API.
Multiparty is a Node.js module for parsing multipart/form-data requests. It is similar to formidable in terms of functionality but has a different API and is known for being more memory efficient, as it streams files to disk instead of buffering them in memory.
A node.js module for parsing form data, especially file uploads.
This module was developed for Transloadit, 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.
keepExtensions: true.Note: Starting with this version, formidable emits 'file' events for empty file input fields. Previously those were incorrectly emitted as regular file input fields with value = "".
'aborted' eventThis marks the beginning of development on version 2.0 which will include several architectural improvements.
'progress' event when receiving data, regardless of parsing it. (Tim Koschützki)Important: The old property names of the File class will be removed in a future release.
These releases were done before starting to maintain the above Changelog:
Via npm:
npm install formidable@latest
Manually:
git clone git://github.com/felixge/node-formidable.git formidable
vim my.js
# var formidable = require('./formidable');
Note: Formidable requires gently to run the unit tests, but you won't need it for just using the library.
Parse an incoming file upload.
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(80);
new formidable.IncomingForm()
Creates a new incoming form.
incomingForm.encoding = 'utf-8'
The encoding to use for incoming form fields.
incomingForm.uploadDir = process.env.TMP || '/tmp' || process.cwd()
The directory for placing file uploads in. You can move them later on using
fs.rename(). The default directory is picked at module load time depending on
the first existing directory from those listed above.
incomingForm.keepExtensions = false
If you want the files written to incomingForm.uploadDir to include the extensions of the original files, set this property to true.
incomingForm.type
Either 'multipart' or 'urlencoded' depending on the incoming request.
incomingForm.maxFieldsSize = 2 * 1024 * 1024
Limits the amount of memory a field (not file) can allocate in bytes.
If this value is exceeded, an 'error' event is emitted. The default
size is 2MB.
incomingForm.bytesReceived
The amount of bytes received for this form so far.
incomingForm.bytesExpected
The expected number of bytes in this form.
incomingForm.parse(request, [cb])
Parses an incoming node.js request containing form data. If cb is provided, all fields an files are collected and passed to the callback:
incomingForm.parse(req, function(err, fields, files) {
// ...
});
incomingForm.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.
incomingForm.onPart = function(part) {
part.addListener('data', function() {
// ...
});
}
If you want to use formidable to only handle certain parts for you, you can do so:
incomingForm.onPart = function(part) {
if (!part.filename) {
// let formidable handle all non-file parts
incomingForm.handlePart(part);
}
}
Check the code in this method for further inspiration.
Event: 'progress' (bytesReceived, bytesExpected)
Emitted after each incoming chunk of data that has been parsed. Can be used to roll your own progress bar.
Event: 'field' (name, value)
Emitted whenever a field / value pair has been received.
Event: 'fileBegin' (name, file)
Emitted whenever a new file is detected in the upload stream. Use this even if you want to stream the file to somewhere else while buffering the upload on the file system.
Event: 'file' (name, file)
Emitted whenever a field / file pair has been received. file is an instance of File.
Event: 'error' (err)
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.
Event: '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. In the future there will be a separate 'timeout' event (needs a change in the node core).
Event: '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.
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.
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.
file.name = null
The name this file had according to the uploading client.
file.type = null
The mime type of this file, according to the uploading client.
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.
Formidable is licensed under the MIT license.
FAQs
A node.js module for parsing form data, especially file uploads.
The npm package formidable receives a total of 9,606,983 weekly downloads. As such, formidable popularity was classified as popular.
We found that formidable demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 5 open source maintainers collaborating on the project.
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