content-disposition

Create and parse HTTP Content-Disposition header

Installation

$ npm install content-disposition

API

import { create, parse, format } from 'content-disposition';

create(filename, options)

Create an attachment Content-Disposition header value using the given file name, if supplied. The filename is optional and if no file name is desired, but you want to specify options, set filename to undefined.

res.setHeader('Content-Disposition', create('∫ maths.pdf'));

note HTTP headers are of the ISO-8859-1 character set. If you are writing this header through a means different from setHeader in Node.js, you'll want to specify the 'binary' encoding in Node.js.

Options

contentDisposition accepts these properties in the options object.

fallback

If the filename option is outside US-ASCII, then the file name is actually stored in a supplemental field for clients that support Unicode file names and a US-ASCII version of the file name is automatically generated.

This specifies the US-ASCII file name to override the automatic generation or disables the generation all together, defaults to true.

• A string will specify the US-ASCII file name to use in place of automatic generation.
• false will disable including a US-ASCII file name and only include the Unicode version (unless the file name is already US-ASCII).
• true will enable automatic generation if the file name is outside US-ASCII.

If the filename option is US-ASCII and this option is specified and has a different value, then the filename option is encoded in the extended field and this set as the fallback field, even though they are both US-ASCII.

type

Specifies the disposition type, defaults to "attachment". This can also be "inline", or any other value (all values except inline are treated like attachment, but can convey additional information if both parties agree to it).

parse(string, options)

const disposition = parse(
  'attachment; filename="EURO rates.txt"; filename*=UTF-8\'\'%e2%82%ac%20rates.txt',
);

Parse a Content-Disposition header string. This automatically handles extended ("Unicode") parameters by decoding them and providing them under the standard parameter name. This will return an object with the following properties:

• type: The disposition type (always lower case). Example: 'attachment'

• parameters: An object of the parameters in the disposition (name of parameter always lower case and extended versions replace non-extended versions). Example: {filename: "€ rates.txt"}

Options

multipart

Parse parameters using browser multipart/form-data behavior.

parse('form-data; name="file"; filename="the %22plans%22.pdf"', {
  multipart: true,
});

extended

Parse RFC 5987 extended header parameters automatically when decoding parameters, defaults to true.

format(obj, options)

const disposition = format({
  type: 'attachment',
  parameters: {
    filename: '€ rates.txt',
  },
});

Formats an object to a Content-Disposition header string. This automatically handles extended ("Unicode") parameters and returns a string. Example: 'attachment; filename*=UTF-8''%E2%82%AC%20rates.txt'

Options

multipart

Format parameters using browser multipart/form-data behavior. This quotes parameter values, escapes " as %22, and writes Unicode values directly instead of using extended parameters.

format(
  {
    type: 'form-data',
    parameters: { name: 'file', filename: '€ rates.txt' },
  },
  { multipart: true },
);

extended

Encode Unicode parameter values using RFC 5987 extended header parameters, e.g. filename*=, defaults to true.

Examples

Send a file for download

import fs from 'node:fs';
import http from 'node:http';
import { create } from 'content-disposition';
import onFinished from 'on-finished';

const filePath = '/path/to/public/plans.pdf';

http.createServer(function onRequest(req, res) {
  // set headers
  res.setHeader('Content-Type', 'application/pdf');
  res.setHeader('Content-Disposition', create(filePath));

  // send file
  const stream = fs.createReadStream(filePath);
  stream.pipe(res);
  onFinished(res, function () {
    stream.destroy();
  });
});

Local demo

Run the upload inspector locally:

npm run demo

Then open http://127.0.0.1:3000 in your browser. The demo lets you upload files, inspect the multipart upload part headers sent by the browser, and compare them with the download Content-Disposition header generated by this package.

Testing

$ npm test

References

• RFC 2616: Hypertext Transfer Protocol -- HTTP/1.1
• RFC 5987: Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters
• RFC 6266: Use of the Content-Disposition Header Field in the Hypertext Transfer Protocol (HTTP)
• RFC 8187: Indicating Character Encoding and Language for HTTP Header Field Parameters
• HTML Living Standard: Multipart form data
• Test Cases for HTTP Content-Disposition header field (RFC 6266) and the Encodings defined in RFCs 2047, 2231 and 5987

License

MIT