https://github.com/lukechilds/expired

Calculate when HTTP cache headers expire
https://github.com/lukechilds/expired

cache headers http

Last synced: 10 days ago
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Calculate when HTTP cache headers expire

• Host: GitHub
• URL: https://github.com/lukechilds/expired
• Owner: lukechilds
• License: mit
• Created: 2016-12-22T11:51:06.000Z (almost 8 years ago)
• Default Branch: master
• Last Pushed: 2021-03-17T19:17:19.000Z (over 3 years ago)
• Last Synced: 2024-10-24T16:53:49.000Z (17 days ago)
• Topics: cache, headers, http
• Language: JavaScript
• Size: 74.2 KB
• Stars: 74
• Watchers: 6
• Forks: 4
• Open Issues: 6
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# expired

> Calculate when HTTP responses expire from the cache headers

[![Build Status](https://travis-ci.org/lukechilds/expired.svg?branch=master)](https://travis-ci.org/lukechilds/expired)

[![Coverage Status](https://coveralls.io/repos/github/lukechilds/expired/badge.svg?branch=master)](https://coveralls.io/github/lukechilds/expired?branch=master)

[![npm](https://img.shields.io/npm/v/expired.svg)](https://www.npmjs.com/package/expired)

`expired` accepts HTTP headers as an argument and will return information on when the resource will expire. `Cache-Control` and `Expires` headers are supported, if both exist `Cache-Control` takes priority ([Why?](http://stackoverflow.com/a/7549558/5625059)).

## Install

```shell

npm install --save expired

```

## Usage

```js

const expired = require('expired');

const headers = `

Age: 0

Cache-Control: public, max-age=300

Content-Encoding: gzip

Content-Type: application/json;charset=utf-8

Date: Fri, 23 Dec 2016 05:50:31 GMT

Last-Modified: Fri, 23 Dec 2016 05:23:23 GMT`;

expired(headers);

// false

expired.in(headers);

// 500000

expired.on(headers);

// Date('2016-12-23T05:55:31.000Z')

delay(600000).then(() => {

  expired(headers);

  // true

  expired.in(headers);

  // -100000

  expired.on(headers);

  // Date('2016-12-23T05:55:31.000Z')

});

```

Many HTTP modules will parse response headers into an object for you. `expired` will also accept headers in this format:

```js

const expired = require('expired');

const headers = {

  'age': '0',

  'cache-control': 'public, max-age=300',

  'content-encoding': 'gzip',

  'content-type': 'application/json;charset=utf-8',

  'date': 'Fri, 23 Dec 2016 05:50:31 GMT',

  'last-modified': 'Fri, 23 Dec 2016 05:23:23 GMT'

};

expired(headers);

// false

```

## Pure Usage

You can make the functions pure by passing in a JavaScript `Date` object to compare to instead of depending on `new Date()`. This isn't necessary for `expired.on` as it doesn't compare dates and is already pure.

The following are all pure functions:

```js

const headers = `...`;

const date = new Date();

expired(headers, date);

expired.in(headers, date);

expired.on(headers);

```

## API

### expired(headers, [date])

Returns a boolean relating to whether the resource has expired or not. `true` means it's expired, `false` means it's fresh.

### expired.in(headers, [date])

Returns the amount of milliseconds from the current date until the resource will expire. If the resource has already expired it will return a negative integer.

### expired.on(headers)

Returns a JavaScript `Date` object for the date the resource will expire.

## License

MIT © Luke Childs