negotiator

What is negotiator?

The negotiator npm package is a content negotiation library used to parse and match HTTP headers for various content types. It allows servers to select the best representation of a resource based on the client's capabilities and preferences, as expressed through HTTP headers.

What are negotiator's main functionalities?

Content-Type Negotiation

This feature allows the server to determine the best media type to respond with, based on the client's 'Accept' HTTP header.

const Negotiator = require('negotiator');
const availableMediaTypes = ['text/html', 'application/json'];
const negotiator = new Negotiator(request);
const bestMediaType = negotiator.mediaType(availableMediaTypes);

Language Negotiation

This feature enables the server to select the best language for the response content based on the client's 'Accept-Language' HTTP header.

const Negotiator = require('negotiator');
const availableLanguages = ['en', 'es', 'fr'];
const negotiator = new Negotiator(request);
const bestLanguage = negotiator.language(availableLanguages);

Encoding Negotiation

This feature allows the server to choose the best encoding for the response based on the client's 'Accept-Encoding' HTTP header.

const Negotiator = require('negotiator');
const availableEncodings = ['gzip', 'deflate'];
const negotiator = new Negotiator(request);
const bestEncoding = negotiator.encoding(availableEncodings);

Charset Negotiation

This feature allows the server to determine the best charset for the response content based on the client's 'Accept-Charset' HTTP header.

const Negotiator = require('negotiator');
const availableCharsets = ['utf-8', 'iso-8859-1'];
const negotiator = new Negotiator(request);
const bestCharset = negotiator.charset(availableCharsets);

Other packages similar to negotiator

accepts

The 'accepts' npm package is similar to 'negotiator' in that it also provides content negotiation capabilities. It is built on top of 'negotiator' and provides a higher-level API for handling 'Accept', 'Accept-Encoding', 'Accept-Language', and 'Accept-Charset' headers.

README

negotiator

An HTTP content negotiator for Node.js

Installation

$ npm install negotiator

API

var Negotiator = require('negotiator')

Accept Negotiation

availableMediaTypes = ['text/html', 'text/plain', 'application/json']

// The negotiator constructor receives a request object
negotiator = new Negotiator(request)

// Let's say Accept header is 'text/html, application/*;q=0.2, image/jpeg;q=0.8'

negotiator.mediaTypes()
// -> ['text/html', 'image/jpeg', 'application/*']

negotiator.mediaTypes(availableMediaTypes)
// -> ['text/html', 'application/json']

negotiator.mediaType(availableMediaTypes)
// -> 'text/html'

You can check a working example at examples/accept.js.

Methods

mediaType()

Returns the most preferred media type from the client.

mediaType(availableMediaType)

Returns the most preferred media type from a list of available media types.

mediaTypes()

Returns an array of preferred media types ordered by the client preference.

mediaTypes(availableMediaTypes)

Returns an array of preferred media types ordered by priority from a list of available media types.

Accept-Language Negotiation

negotiator = new Negotiator(request)

availableLanguages = ['en', 'es', 'fr']

// Let's say Accept-Language header is 'en;q=0.8, es, pt'

negotiator.languages()
// -> ['es', 'pt', 'en']

negotiator.languages(availableLanguages)
// -> ['es', 'en']

language = negotiator.language(availableLanguages)
// -> 'es'

You can check a working example at examples/language.js.

Methods

language()

Returns the most preferred language from the client.

language(availableLanguages)

Returns the most preferred language from a list of available languages.

languages()

Returns an array of preferred languages ordered by the client preference.

languages(availableLanguages)

Returns an array of preferred languages ordered by priority from a list of available languages.

Accept-Charset Negotiation

availableCharsets = ['utf-8', 'iso-8859-1', 'iso-8859-5']

negotiator = new Negotiator(request)

// Let's say Accept-Charset header is 'utf-8, iso-8859-1;q=0.8, utf-7;q=0.2'

negotiator.charsets()
// -> ['utf-8', 'iso-8859-1', 'utf-7']

negotiator.charsets(availableCharsets)
// -> ['utf-8', 'iso-8859-1']

negotiator.charset(availableCharsets)
// -> 'utf-8'

You can check a working example at examples/charset.js.

Methods

charset()

Returns the most preferred charset from the client.

charset(availableCharsets)

Returns the most preferred charset from a list of available charsets.

charsets()

Returns an array of preferred charsets ordered by the client preference.

charsets(availableCharsets)

Returns an array of preferred charsets ordered by priority from a list of available charsets.

Accept-Encoding Negotiation

availableEncodings = ['identity', 'gzip']

negotiator = new Negotiator(request)

// Let's say Accept-Encoding header is 'gzip, compress;q=0.2, identity;q=0.5'

negotiator.encodings()
// -> ['gzip', 'identity', 'compress']

negotiator.encodings(availableEncodings)
// -> ['gzip', 'identity']

negotiator.encoding(availableEncodings)
// -> 'gzip'

You can check a working example at examples/encoding.js.

Methods

encoding()

Returns the most preferred encoding from the client.

encoding(availableEncodings)

Returns the most preferred encoding from a list of available encodings.

encodings()

Returns an array of preferred encodings ordered by the client preference.

encodings(availableEncodings)

Returns an array of preferred encodings ordered by priority from a list of available encodings.

See Also

The accepts module builds on this module and provides an alternative interface, mime type validation, and more.

License

MIT