Monitoring cache usage with the JavaScript Cache API

23 Oct 2023

References

Caching is a common technique used in web development to improve the performance and speed of a website. The JavaScript Cache API provides a simple and efficient way to store and retrieve files and data in the browser’s cache, reducing the need for repeated network requests.

While caching can significantly improve the user experience, it’s important to monitor the cache usage to ensure that it is working as expected and to troubleshoot any potential issues. In this blog post, we will explore how you can monitor cache usage using the JavaScript Cache API.

Introduction to Cache API
Monitoring Cache Usage
Example Code
Conclusion

Introduction to Cache API

The Cache API, introduced in the Service Worker specification, allows you to create and manage caches in the browser. It provides a programmatic way to store and retrieve files, responses, and other data, making it ideal for caching static assets such as CSS stylesheets, JavaScript files, and images.

To use the Cache API, you first need to check if it is supported by the browser using the caches global object:

if ('caches' in window) {
  // Cache API is supported
}

Once you have verified the support, you can open a cache using the caches.open() method:

caches.open('my-cache').then(function(cache) {
  // Cache is now open and ready to use
});

Monitoring Cache Usage

To monitor cache usage, you can use the CacheStorage interface provided by the Cache API. This interface allows you to access information about the caches available in the browser and perform operations on them.

To retrieve a list of all the caches currently available, you can use the caches.keys() method:

caches.keys().then(function(cacheNames) {
  // Iterate through the cacheNames array
  cacheNames.forEach(function(cacheName) {
    // Log each cache name
    console.log(cacheName);
  });
});

This will log the names of all the caches currently stored in the browser’s cache.

You can also retrieve information about a specific cache using the caches.open() method:

caches.open('my-cache').then(function(cache) {
  // Get information about the cache
  cache.matchAll().then(function(responses) {
    // Log the number of items in the cache
    console.log(responses.length);
  });
});

This will log the number of items currently stored in the ‘my-cache’ cache.

By monitoring cache usage, you can keep track of the number of items stored in a cache, monitor cache size, and troubleshoot any potential caching issues.

Example Code

Here’s a simple example that demonstrates how to monitor cache usage:

if ('caches' in window) {
  caches.open('my-cache').then(function(cache) {
    // Get information about the cache
    cache.keys().then(function(requests) {
      console.log('Number of items in cache:', requests.length);
    });
  });
}

Conclusion

Monitoring cache usage is an essential part of optimizing the performance of a website. By using the JavaScript Cache API, you can easily retrieve information about the caches available in the browser and monitor their usage. This allows you to troubleshoot any caching issues and ensure that your website is making the most of caching to deliver a faster and smoother user experience.

Remember to periodically check the cache size, number of items, and perform any necessary cache management to ensure optimal performance.

#References

Table of Contents

Introduction to Cache API

Monitoring Cache Usage

Example Code

Conclusion