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.
Maintainers Wanted: Please see https://github.com/felixge/node-formidable/issues/412
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.
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 does not include any multipart handling, nor does body-parser.
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(8080);
var form = new formidable.IncomingForm()
Creates a new incoming form.
form.encoding = 'utf-8';
Sets encoding for incoming form fields.
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().
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.
form.type
Either 'multipart' or 'urlencoded' depending on the incoming request.
form.maxFieldsSize = 2 * 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 2MB.
form.maxFields = 1000;
Limits the number of fields that the querystring parser will decode. Defaults to 1000 (0 for unlimited).
form.hash = false;
If you want checksums calculated for incoming files, set this to either 'sha1' or 'md5'.
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.
form.bytesReceived
The amount of bytes received for this form so far.
form.bytesExpected
The expected number of bytes in this form.
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:
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.
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:
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.
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.
file.hash = null
If hash calculation was set, you can read the hex digest out of this var.
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.
Emitted after each incoming chunk of data that has been parsed. Can be used to roll your own progress bar.
form.on('progress', function(bytesReceived, bytesExpected) {
});
Emitted whenever a field / value pair has been received.
form.on('field', function(name, value) {
});
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.
form.on('fileBegin', function(name, file) {
});
Emitted whenever a field / file pair has been received. file is an instance of File.
form.on('file', function(name, file) {
});
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.
form.on('error', function(err) {
});
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).
form.on('aborted', function() {
});
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.
buffer.write order of arguments for Node 7 (Kornel Lesiński)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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