When you're developing web applications, using XMLHttpRequests (XHRs) is a common practice to fetch data asynchronously, making your web pages more dynamic and interactive. However, sometimes you might want to know if your XMLHttpRequest request hit the browser cache to optimize performance. In this article, I'll walk you through how to determine if an XMLHttpRequest hit the browser cache or not.
When an XHR request is made, the browser first checks its cache to see if it has the requested resource stored locally. If the resource is found in the cache, the browser can retrieve it quickly without making a full request to the server. This can significantly speed up your web application by reducing network latency and server load.
To check if an XMLHttpRequest request hit the browser cache, you can inspect the response headers that are returned when the request completes. Specifically, you should look at the "X-Cache" header, which provides information about how the response was cached by the browser.
If the "X-Cache" header contains the value "HIT," it means that the response was served from the browser cache. This indicates that the request did not go to the server, and the data was retrieved locally. On the other hand, if the "X-Cache" header shows "MISS," it means that the response was not found in the cache, and the request went to the server to fetch the data.
To view the response headers in your browser's developer tools, follow these steps:
1. Open the developer tools in your browser (usually by pressing F12 or right-clicking on the webpage and selecting "Inspect").
2. Navigate to the "Network" tab.
3. Trigger the XMLHttpRequest request in your web application.
4. Look for the specific XHR request in the network log, then click on it to view the detailed information.
5. In the headers section of the request, you should see the "X-Cache" header and its corresponding value.
By checking the value of the "X-Cache" header, you can determine whether your XMLHttpRequest request hit the browser cache or not. This information is valuable for optimizing your web application's performance, as it helps you understand how caching is affecting the retrieval of resources.
In conclusion, being able to tell if an XMLHttpRequest hit the browser cache is essential for improving the efficiency and speed of your web applications. By monitoring the "X-Cache" header in the response headers, you can easily identify whether your requests are utilizing the cache effectively. This knowledge empowers you to make informed decisions on caching strategies and ultimately deliver a better user experience on your web applications.