express-cache-response-directive


Middleware for ExpressJS that defines a cacheControl method to set Cache-Control headers.

This middleware doesn't define legacy Expires headers. For compatibility with old HTTP/1.0 agents combine it with express-legacy-expires.

Install

``bash
npm install express-cache-response-directive
`

Usage

`js
const cacheResponseDirective = require('express-cache-response-directive');
`

`js
app.use(cacheResponseDirective());
`

`js
app.get('/', function(req, res, next) {
res.cacheControl({maxAge: 300});
// ...
});
`

$3

The method added by the middleware accepts an optional string pattern and an object of Cache-Control options. Both are optional but at least one of them should be specified.

See the HTTP/1.1 Standard's Cache-Control sections for information on the usage of Cache-Control directives.

#### Patterns

String patterns are defined for simple directives so you can simply write res.cacheControl("public"); instead of having to always write res.cacheControl({'public': true});. Patterns can be combined with options res.cacheControl("public", {mustRevalidate: true});.

##### "public"

`js
res.cacheControl("public");
// Cache-Control: public
`

##### "private"

`js
res.cacheControl("private");
// Cache-Control: private
`

##### "no-cache"

`js
res.cacheControl("no-cache");
// Cache-Control: no-cache
`

##### "no-store"

`js
res.cacheControl("no-store");
// Cache-Control: no-cache, no-store
`

#### Options

Each Cache-Control response directive defined in HTTP/1.1 has an option that can be defined.

- Options for directives that use a delta time accept a number as a value.
- Time values may also be expressed as strings like "3 min", "1h", "5 days".
- Options that optionally accept field names accept true for the normal non-field directive and for the with field-name directive accept either a string or an array of strings for the field names.
- The remaining directives that don't have a value simply accept a truthy value.

The public, private, no-cache, and no-store directives are exclusive only one may be specified. With the exception that no-cache and no-store may be defined together.

##### public

`js
res.cacheControl({'public': true});
// Cache-Control: public
`

##### private

`js
res.cacheControl({'private': true});
// Cache-Control: private
`

`js
res.cacheControl({'private': "X-Private"});
// Cache-Control: private="X-Private"
`

`js
res.cacheControl({'private': ["X-Private-1", "X-Private-2"]});
// Cache-Control: private="X-Private-1, X-Private-2"
`

##### no-cache

`js
res.cacheControl({'no-cache': true});
res.cacheControl({noCache: true});
// Cache-Control: no-cache
`

`js
res.cacheControl({noCache: "X-Uncached"});
// Cache-Control: no-cache="X-Uncached"
`

`js
res.cacheControl({noCache: ["X-Uncached-1", "X-Uncached-2"]});
// Cache-Control: no-cache="X-Uncached-1, X-Uncached-2"
`

##### no-store

`js
res.cacheControl({'no-store': true});
res.cacheControl({noStore: true});
// Cache-Control: no-cache, no-store
`

- no-store also implies no-cache because some browsers have begun treating no-cache the same way they treat no-store.

##### max-age

`js
res.cacheControl({'max-age': 300});
res.cacheControl({maxAge: 300});
res.cacheControl({maxAge: "5min"});
// Cache-Control: public, max-age=300
`

- max-age implies public if none of private, no-cache, or no-store is defined, so you can define it alone.

##### s-maxage

`js
res.cacheControl({'s-maxage': 300});
res.cacheControl({sMaxage: 300});
res.cacheControl({sMaxAge: 300});
// Cache-Control: public, s-maxage=300
`

- s-maxage supports sMaxAge in addition to the standard camel-case conversion sMaxage due to the potential confusion of the max-age to maxAge conversion.

##### must-revalidate

`js
res.cacheControl({'must-revalidate': true});
res.cacheControl({mustRevalidate: true});
// Cache-Control: must-revalidate
`

##### proxy-revalidate

`js
res.cacheControl({'proxy-revalidate': true});
res.cacheControl({proxyRevalidate: true});
// Cache-Control: proxy-revalidate
`

##### no-transform

`js
res.cacheControl({noTransform: true});
res.cacheControl({'no-transform': true});
// Cache-Control: no-transform
``

License

MIT