javascript/jquery - recognize loaded from cache

Question

I have image gallery and am updating front-end, is there a way to use javascript or jquery or any other front end technology to identify which image was loaded from cache? I would like to apply additional class for those items.

Thanks for any sugestions.

Possible duplicate of How to tell if an image is loaded or cached in JQuery? — BenM
– BenM, Commented Oct 6, 2015 at 12:12

Remy Grandin · Accepted Answer · 2015-10-06 12:17:37Z

3

Short answer :

No

Long answer :

No, and there is a reason for that : If you could know which element of tha page was from the cache, you could deduce that your user have been to the same page or another page with the same element/ressource. It would be a massive potential privacy breach.

A similar problem was arised with the changing color of link if they are visited (see http://dbaron.org/mozilla/visited-privacy for more info)

edited Oct 6, 2015 at 12:17

answered Oct 6, 2015 at 12:15

Remy Grandin

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4 Comments

Maurice Perry Over a year ago

Well Özgur's answer shows that this privacy breach does nonetheless exist.

Remy Grandin Over a year ago

No, the image.complete only said if the image have finished loading, it does not tell if the image was loaded from cache or from a remote server

Maurice Perry Over a year ago

As javascript is not multithreaded, there is a good chance that if image.complete is true immediatly after setting the src attribute, the image was loaded from the cache.

Maurice Perry Over a year ago

That said, I haven't checked that the code actually works.

Özgür Kaplan · Accepted Answer · 2015-10-06 12:15:04Z

1

You can use the function below. However it will load the image if not cached.

function isCached(src) {
    var image = new Image();
    image.src = src;
    return image.complete;
}

answered Oct 6, 2015 at 12:15

Özgür Kaplan

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2 Comments

Remy Grandin Over a year ago

This will only tell of the image is loaded, not if it is loaded from cache

Özgür Kaplan Over a year ago

@RemyGrandin You are right. But if image.complete is true after setting src it's most likely was loaded from the cache.

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