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+# 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