Progressive Web Application Development by Example

Purging stale responses using time to live

The next cache invalidation strategy is based on how long a response can be cached. If you don't have access to the Cache-Control header, it may be challenging to determine how long to cache the response.

The good news is that the Cache-Control header is not the only way to determine a response's cache lifespan. When responses are added to a named cache, a "date" value is added. You can use the cached date value to apply a timeout rule to the cached responses:

let responseDate = new Date(response.headers.get("date")), 
  currentDate = Date.now(); 
 
if(!DateManager.compareDates(currentDate,  
  DateManager.addSecondsToDate(responseDate, 300))) { 
    cache.add(request); 
}else{ 
    cache.delete(request); 
} 

When a cached ...