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vary

Manipulate the HTTP Vary header

# Installation

This is a Node.js module available through the npm registry. Installation is done using the `npm install` command:

$ npm install vary

# API

var vary = require('vary')

## vary(res, field)

Adds the given header `field` to the `Vary` response header of `res`. This can be a string of a single field, a string of a valid `Vary` header, or an array of multiple fields.

This will append the header if not already listed, otherwise leaves it listed in the current location.

// Append "Origin" to the Vary header of the response
vary(res, 'Origin')

## vary.append(header, field)

Adds the given header `field` to the `Vary` response header string `header`. This can be a string of a single field, a string of a valid `Vary` header, or an array of multiple fields.

This will append the header if not already listed, otherwise leaves it listed in the current location. The new header string is returned.

// Get header string appending "Origin" to "Accept, User-Agent"
vary.append('Accept, User-Agent', 'Origin')

# Examples

## Updating the Vary header when content is based on it

var http = require('http')
var vary = require('vary')
http.createServer(function onRequest (req, res) {
// about to user-agent sniff
vary(res, 'User-Agent')
var ua = req.headers['user-agent'] || ''
var isMobile = /mobi|android|touch|mini/i.test(ua)
// serve site, depending on isMobile
res.setHeader('Content-Type', 'text/html')
res.end('You are (probably) ' + (isMobile ? '' : 'not ') + 'a mobile user')
})

# Testing

$ npm test

# License

[MIT](LICENSE)