PerformanceResourceTiming: deliveryType property

The deliveryType property can have the following values:.

cache

If the resource was retrieved from the cache

"" (empty string)

If none of the other defined delivery types

This set of delivery types is expected to be expanded in the future — for example, to indicate preloaded resources and to indicate prefetched navigation requests.

The deliveryType property can be used to get specific resource timing entries only; for example, only those that were cached.

The following example uses a PerformanceObserver to notify of new resource performance entries as they are recorded in the browser's performance timeline. The buffered option is used for accessing entries from before the observer creation.

const observer = new PerformanceObserver((list) => {
  const cachedResources = list.getEntries().filter((entry) => {
    return entry.deliveryType === "cache";
  });
  console.log(cachedResources);
});

observer.observe({ type: "resource", buffered: true });

The following example uses Performance.getEntriesByType(), which only shows resource performance entries present in the browser's performance timeline at the time you call the method.

const scripts = performance.getEntriesByType("resource").filter((entry) => {
  return entry.deliveryType === "cache";
});
console.log(scripts);