Fresh
HTTP response freshness testing
Table of Contents
Getting Started
Prerequisites
- Node.js 8 or higher is required.
Installation
npm i -s fresh
Usage
- TypeScript:
import fresh from "fresh";
- JavaScript:
const fresh = require("fresh").default;
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 receive 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 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
const reqHeaders = { "if-none-match": '"foo"' };
const resHeaders = { etag: '"bar"' };
fresh(reqHeaders, resHeaders);
// => false
const reqHeaders = { "if-none-match": '"foo"' };
const resHeaders = { etag: '"foo"' };
fresh(reqHeaders, resHeaders);
// => true
Using with Node.js http server
import fresh from "fresh";
import http from "http";
const server = http.createServer((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;
return res.end();
}
// 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);
Benchmarks
npm run benchmarks
Versioning
We use SemVer for versioning. For the versions available, see the tags on this repository.
Changelog
See the CHANGELOG.md file for details
Authors
- Ardalan Amini - Core Maintainer - @ardalanamini
See also the list of contributors who participated in this project.
License
This project is licensed under the MIT License - see the LICENSE file for details