forked from zhurui/management
120 lines
3.3 KiB
Markdown
120 lines
3.3 KiB
Markdown
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# fresh
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[![NPM Version][npm-image]][npm-url]
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[![NPM Downloads][downloads-image]][downloads-url]
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[![Node.js Version][node-version-image]][node-version-url]
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[![Build Status][travis-image]][travis-url]
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[![Test Coverage][coveralls-image]][coveralls-url]
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HTTP response freshness testing
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## Installation
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This is a [Node.js](https://nodejs.org/en/) module available through the
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[npm registry](https://www.npmjs.com/). Installation is done using the
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[`npm install` command](https://docs.npmjs.com/getting-started/installing-npm-packages-locally):
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```
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$ npm install fresh
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```
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## API
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<!-- eslint-disable no-unused-vars -->
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```js
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var fresh = require('fresh')
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```
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### fresh(reqHeaders, resHeaders)
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Check freshness of the response using request and response headers.
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When the response is still "fresh" in the client's cache `true` is
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returned, otherwise `false` is returned to indicate that the client
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cache is now stale and the full response should be sent.
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When a client sends the `Cache-Control: no-cache` request header to
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indicate an end-to-end reload request, this module will return `false`
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to make handling these requests transparent.
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## Known Issues
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This module is designed to only follow the HTTP specifications, not
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to work-around all kinda of client bugs (especially since this module
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typically does not recieve enough information to understand what the
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client actually is).
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There is a known issue that in certain versions of Safari, Safari
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will incorrectly make a request that allows this module to validate
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freshness of the resource even when Safari does not have a
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representation of the resource in the cache. The module
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[jumanji](https://www.npmjs.com/package/jumanji) can be used in
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an Express application to work-around this issue and also provides
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links to further reading on this Safari bug.
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## Example
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### API usage
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<!-- eslint-disable no-redeclare, no-undef -->
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```js
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var reqHeaders = { 'if-none-match': '"foo"' }
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var resHeaders = { 'etag': '"bar"' }
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fresh(reqHeaders, resHeaders)
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// => false
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var reqHeaders = { 'if-none-match': '"foo"' }
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var resHeaders = { 'etag': '"foo"' }
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fresh(reqHeaders, resHeaders)
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// => true
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```
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### Using with Node.js http server
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```js
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var fresh = require('fresh')
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var http = require('http')
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var server = http.createServer(function (req, res) {
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// perform server logic
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// ... including adding ETag / Last-Modified response headers
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if (isFresh(req, res)) {
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// client has a fresh copy of resource
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res.statusCode = 304
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res.end()
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return
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}
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// send the resource
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res.statusCode = 200
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res.end('hello, world!')
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})
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function isFresh (req, res) {
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return fresh(req.headers, {
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'etag': res.getHeader('ETag'),
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'last-modified': res.getHeader('Last-Modified')
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})
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}
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server.listen(3000)
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```
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## License
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[MIT](LICENSE)
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[npm-image]: https://img.shields.io/npm/v/fresh.svg
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[npm-url]: https://npmjs.org/package/fresh
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[node-version-image]: https://img.shields.io/node/v/fresh.svg
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[node-version-url]: https://nodejs.org/en/
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[travis-image]: https://img.shields.io/travis/jshttp/fresh/master.svg
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[travis-url]: https://travis-ci.org/jshttp/fresh
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[coveralls-image]: https://img.shields.io/coveralls/jshttp/fresh/master.svg
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[coveralls-url]: https://coveralls.io/r/jshttp/fresh?branch=master
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[downloads-image]: https://img.shields.io/npm/dm/fresh.svg
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[downloads-url]: https://npmjs.org/package/fresh
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