How to bypass lazy load if the image is already cached

Question

I am using jQuery lazy loading to lazy load images on my website and it is great BUT the problem is that if the user comes 10 times to the website, the image lazy loads 10 times.

How can I cache the image and make it lazy load only once and the rest displayed directly from the cache?

In general the js code to lazy load is

$(function($) {
    $("img.lazy").Lazy();
});

And from there any image with class lazy, lazy loads. For example the two example below will lazy load the image

<img src="myimage1.png" class="lazy">
<img data-src="myimage2.png" class="lazy">

And below is the source code that lazy loads. How can I cache the image and make it lazy load only once and the rest displayed directly from the cache?

/*! jQuery & Zepto Lazy v1.7.10 - http://jquery.eisbehr.de/lazy - MIT&GPL-2.0 license - Copyright 2012-2018 Daniel 'Eisbehr' Kern */
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Answer 1

TL;DR

There is no need to do something like you have in mind, because Lazy will use the browser cache by itself.

---

There are two things to know about your question I like to answer separately.

A way to check if an image is cached by the browser

If you would like to have a different behavior for cached images on your page, you would need to know what image is cached before rendering the page, or after rendering with JS. But there is no function I would know, to check a browser cache in server-side. So this is not an option.

There are some ways / hacks to check an image cache in JS. But whenever you check, the image will be fully loaded by the browser. That means, at the moment you check if an image is cached, you already load it and it will be cached too. So this will not get you any further.

Lazy will rely on the browser cache

But there is one thing that makes the thing you want to archive unnecessary. Lazy will use the browser cache too. Whenever an image is loaded, (and caching is enabled) the browser will cache it. There is no difference between plain HTML and loading via JS. That said, if an image is cached by the browser, Lazy will load the cached image and just show it.

As you see, it will use cached images too, but with the possibility to use all features of Lazy, like effects and everything else. So there is no need for any change on your side.

I hope this will help you.