albertyw/ajax-cache-parser

ajax-cache-parser
=================

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A small function to get when an ajax request expires

Given an XMLHttpRequest object that has received response headers back from a server, `getCacheExpiry` will return
a javascript `Date` object that represents when the response will expire based on the `Expires` and `Cache-Control`
response headers.  If caching headers are not present or are unparseable, `undefined` will be returned.  If caching
headers indicate that the resource should not be cached, `null` will be returned.

Example
-------
```javascript
function callback(){
  var expiration = parser.getCacheExpiry(this);
  // do something with expiration
}
var oReq = new XMLHttpRequest();
oReq.onload = callback;
oReq.open("get", yourUrl, true);
oReq.send();
```

Information about caching headers comes from: https://www.mnot.net/cache_docs/