Negotiate.js

1.0.1 verified Sat Apr 25 auth: no javascript maintenance

JavaScript implementation of the HTTP preemptive content negotiation algorithm as defined in the original HTTP 1.1 draft spec. Stable version 1.0.1, no longer actively developed. Differentiators: implements the original draft negotiation algorithm (not the final RFC), handles media type, language, charset, and encoding negotiation. Suitable for Node.js HTTP servers needing automatic variant selection. Alternative to content-negotiation libraries that follow the final RFC.

Common errors

error Negotiate is not defined ↓

cause Using the library without importing it first.

fix

Add const Negotiate = require('negotiate'); or import Negotiate from 'negotiate'; at the top of your file.

error Cannot find module 'negotiate' ↓

cause Package not installed or missing from node_modules.

fix

Run npm install negotiate --save to install the package.

error TypeError: variants is not iterable ↓

cause Passing a single object instead of an array of variants.

fix

Wrap your variant in an array: Negotiate.choose([variant], request);

Warnings

gotcha The algorithm implements the original HTTP 1.1 draft spec, not the final RFC 7231. Results may differ from other content negotiation libraries. ↓

fix Ensure your expected negotiation behavior matches the draft algorithm; test with various Accept headers.

gotcha The package has not been updated since 2015 and depends on older Node.js patterns. No security patches have been applied. ↓

fix Consider using an actively maintained alternative like 'content-negotiator' or implement RFC 7231 negotiation yourself.

gotcha Variant quality factor defaults to 1.0 if not specified, which may cause unexpected selections if you omit quality values. ↓

fix Always explicitly set the quality property on each variant to control priority.

Install

npm install negotiate

yarn add negotiate

pnpm add negotiate

Imports

Negotiate
wrong
```
const Negotiate = require('negotiate')
```
correct
```
import Negotiate from 'negotiate'
```
ESM default import; CommonJS require works but is not the recommended pattern
choose
wrong
```
const { choose } = require('negotiate')
```
correct
```
import { choose } from 'negotiate'
```
Named export for the choose function; prefer named import for clarity.
Negotiate
wrong
```
import { Negotiate } from 'negotiate'
```
correct
```
const Negotiate = require('negotiate')
```
CommonJS require gets the default export; named import with braces will not work.

Quickstart

Shows how to define variants and select the best representation for an HTTP request using negotiate.choose().

import Negotiate from 'negotiate';

const variants = [
  {
    method: 'GET',
    type: 'text/html',
    language: 'en-ca',
    charset: 'iso-8859-1',
    encoding: null,
    quality: 1.0,
    length: 36741,
    filename: 'blog.html'
  },
  {
    method: 'GET',
    type: 'application/atom+xml',
    language: 'en',
    charset: 'utf-8',
    encoding: 'gzip',
    quality: 0.8,
    length: 12987,
    filename: 'blog.atom.gzip'
  }
];

const request = {
  url: '/blog',
  method: 'GET',
  headers: {
    'accept': 'application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5',
    'accept-language': 'en-US,en;q=0.8',
    'accept-encoding': 'gzip,deflate,sdch',
    'accept-charset': 'ISO-8859-1,utf-8;q=0.7,*;q=0.3'
  }
};

const responses = Negotiate.choose(variants, request);
console.log(responses[0]);