HORIZON PROJECT

# fresh

[![NPM Version][npm-image]][npm-url]

[![NPM Downloads][downloads-image]][downloads-url]

[![Node.js Version][node-version-image]][node-version-url]

[![Build Status][travis-image]][travis-url]

[![Test Coverage][coveralls-image]][coveralls-url]

HTTP response freshness testing

## Installation

This is a [Node.js](https://nodejs.org/en/) module available through the

[npm registry](https://www.npmjs.com/). Installation is done using the

[`npm install` command](https://docs.npmjs.com/getting-started/installing-npm-packages-locally):

```

$ npm install fresh

```

## API

<!-- eslint-disable no-unused-vars -->

```js

var fresh = require('fresh')

```

### fresh(reqHeaders, resHeaders)

Check freshness of the response using request and response headers.

When the response is still "fresh" in the client's cache `true` is

returned, otherwise `false` is returned to indicate that the client

cache is now stale and the full response should be sent.

When a client sends the `Cache-Control: no-cache` request header to

indicate an end-to-end reload request, this module will return `false`

to make handling these requests transparent.

## Known Issues

This module is designed to only follow the HTTP specifications, not

to work-around all kinda of client bugs (especially since this module

typically does not recieve enough information to understand what the

client actually is).

There is a known issue that in certain versions of Safari, Safari

will incorrectly make a request that allows this module to validate

freshness of the resource even when Safari does not have a

representation of the resource in the cache. The module

[jumanji](https://www.npmjs.com/package/jumanji) can be used in

an Express application to work-around this issue and also provides

links to further reading on this Safari bug.

## Example

### API usage

<!-- eslint-disable no-redeclare, no-undef -->

```js

var reqHeaders = { 'if-none-match': '"foo"' }

var resHeaders = { 'etag': '"bar"' }

fresh(reqHeaders, resHeaders)

// => false

var reqHeaders = { 'if-none-match': '"foo"' }

var resHeaders = { 'etag': '"foo"' }

fresh(reqHeaders, resHeaders)

// => true

```

### Using with Node.js http server

```js

var fresh = require('fresh')

var http = require('http')

var server = http.createServer(function (req, res) {

  // perform server logic

  // ... including adding ETag / Last-Modified response headers

  if (isFresh(req, res)) {

    // client has a fresh copy of resource

    res.statusCode = 304

    res.end()

    return

  }

  // send the resource

  res.statusCode = 200

  res.end('hello, world!')

})

function isFresh (req, res) {

  return fresh(req.headers, {

    'etag': res.getHeader('ETag'),

    'last-modified': res.getHeader('Last-Modified')

  })

}

server.listen(3000)

```

## License

[MIT](LICENSE)

[npm-image]: https://img.shields.io/npm/v/fresh.svg

[npm-url]: https://npmjs.org/package/fresh

[node-version-image]: https://img.shields.io/node/v/fresh.svg

[node-version-url]: https://nodejs.org/en/

[travis-image]: https://img.shields.io/travis/jshttp/fresh/master.svg

[travis-url]: https://travis-ci.org/jshttp/fresh

[coveralls-image]: https://img.shields.io/coveralls/jshttp/fresh/master.svg

[coveralls-url]: https://coveralls.io/r/jshttp/fresh?branch=master

[downloads-image]: https://img.shields.io/npm/dm/fresh.svg

[downloads-url]: https://npmjs.org/package/fresh