# content-disposition

[![NPM Version][npm-image]][npm-url]
[![NPM Downloads][downloads-image]][downloads-url]
[![Node.js Version][node-version-image]][node-version-url]
[![Build Status][github-actions-ci-image]][github-actions-ci-url]
[![Test Coverage][coveralls-image]][coveralls-url]

Create and parse HTTP `Content-Disposition` header

## Installation

```sh
$ npm install content-disposition
```

## API

```js
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`.

```js
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)

```js
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.

```js
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)

```js
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.

```js
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

```js
const contentDisposition = require('content-disposition');
const fs = require('fs');
const http = require('http');
const onFinished = require('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', contentDisposition(filePath));

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

## Local demo

Run the upload inspector locally:

```sh
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

```sh
$ npm test
```

## References

- [RFC 2616: Hypertext Transfer Protocol -- HTTP/1.1][rfc-2616]
- [RFC 5987: Character Set and Language Encoding for Hypertext Transfer Protocol (HTTP) Header Field Parameters][rfc-5987]
- [RFC 6266: Use of the Content-Disposition Header Field in the Hypertext Transfer Protocol (HTTP)][rfc-6266]
- [Test Cases for HTTP Content-Disposition header field (RFC 6266) and the Encodings defined in RFCs 2047, 2231 and 5987][tc-2231]

[rfc-2616]: https://datatracker.ietf.org/doc/html/rfc2616
[rfc-5987]: https://datatracker.ietf.org/doc/html/rfc5987
[rfc-6266]: https://datatracker.ietf.org/doc/html/rfc6266
[tc-2231]: http://greenbytes.de/tech/tc2231/

## License

[MIT](LICENSE)

[npm-image]: https://img.shields.io/npm/v/content-disposition
[npm-url]: https://www.npmjs.com/package/content-disposition
[node-version-image]: https://img.shields.io/node/v/content-disposition
[node-version-url]: https://nodejs.org/en/download
[coveralls-image]: https://img.shields.io/coverallsCoverage/github/jshttp/content-disposition
[coveralls-url]: https://coveralls.io/github/jshttp/content-disposition?branch=master
[downloads-image]: https://img.shields.io/npm/dm/content-disposition
[downloads-url]: https://www.npmjs.com/package/content-disposition
[github-actions-ci-image]: https://img.shields.io/github/actions/workflow/status/jshttp/content-disposition/ci.yml
[github-actions-ci-url]: https://github.com/jshttp/content-disposition/actions/workflows/ci.yml