How to set up image cache in nodejs

In modern websites, images play a vital role. In addition to being beautiful, they can also optimize your website's speed and performance. However, redownloading images every time a user visits your site can lead to slow loading times. This is what image caching does. In this article, we’ll explore how to set up image caching to optimize your Node.js website.

What is image caching?

Image caching refers to storing downloaded images in local storage to avoid re-downloading the same images every time the user visits the website. By reducing the number of times you have to re-download images, you can greatly improve your website's loading speed. When the user visits the page again, the browser will first check whether the same image already exists in local storage. If present, the image is loaded directly from local storage rather than re-downloaded from the server.

Set up image caching

To set up image caching, we need to use HTTP headers to inform the browser when new images should be loaded, and when already cached images should be loaded. This can be achieved using the Cache-Control and Expires headers.

The Cache-Control header is the most widely used option and allows you to specify per-resource caching behavior. By setting Cache-Control in the response header, you can tell the browser how long to cache the resource, or tell the browser under what conditions the resource should be cached.

// Sample code: Let the browser cache static resource files for one year
app.use(express.static('public', { maxAge: '1y' }))

This code tells the browser to cache static resource files for one year. In this way, when a user visits the website for the first time, all static resource files will be cached and then will not need to be downloaded again in the next year.

Another way to set up image caching is to use the Expires header. You can use Expires to tell the browser when it should expire and re-download the resource. Expires is a method used in HTTP 1.0 that tells the browser when it should reacquire resources.

// Sample code: Set the image cache time to one year
app.get('/images/:name', function(req, res, next) {
res.setHeader(' Expires', new Date(Date.now() 31536000000).toUTCString())
next();
})

This code tells the browser to cache this image within one year. It should be noted that Expires is an absolute time, so it has time zone issues. We need to convert the time to UTC time using toUTCString() method to avoid time zone issues.

Summary

In this article, we discussed how to set up image caching to improve the performance of your Node.js web application. We explained the Cache-Control and Expires headers and provided code examples to help you set up image caching behavior. By using these technologies, you can significantly reduce website loading time, reduce bandwidth consumption, and provide users with a better experience. At the same time, we also need to remember that the cache has a lifetime, so the cache needs to be cleared at the appropriate time to ensure the freshness of the content.

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