Image preload trick for javascript slideshows

Preventing Image Delay in a Slideshow

If you can write in html and css and have used images on a site and especially in a slideshow, you may have noticed an annoying delay in the display of the images. Well, I think I've discovered why and THE FIX .

It's actually quite easy.

I noticed that the only image in the slideshow that had no delay was the one used as an image(latest member's thumbnail) in another part of the page. This got me thinking.

I concluded that this image file was being cached but the others were still depending on server requests which takes longer and would account for the delay.

I decided to put all the images in the slideshow in a hidden cell in the page and see what happened.

Sure enough it worked first time! I was elated as I had got rid of the delay plaguing my slideshow.

Given that browsers are being built for speed and that images are notorious for slowing download times I concluded that these images are all now being cached by the browser.

Putting this another way, today's browsers try to keep cached copies to speed up download so it makes sense that I'd fixed the delay problem by creating a non-displaying cell containing the image files.

A working page can have span (<span>), div(div) or table cell(td) that has the id "hide" .Using css in the head you can define id "hide" as display:none.

That's it! It is that simple.

You'll see all the image files in the slideshow have been "preloaded" in this hidden span. They are not displayed in this section of the page but nevertheless they seem to still be cached by the browser resulting in my slideshow no longer having images with a delay.

Instead of server requests, the slideshow is now working off the cached image files - at least that's what I conclude has happened but all I really know is that it worked and that's what matters most so I'm sticking with my story!

Hope this helps any other web developers working with slideshow images.

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Comments 9 comments

psychicdog.net profile image

psychicdog.net 6 years ago Author

Thanks for the update Michael. For the record, I have experienced I.E. 8 browser problems with slideshows containing a large number of images. I once fixed this by changing my browser setting to AUTOMATICALLY for newer versions of webpages (tools>internet options>general settings>browsing history>settings)from the presumably more taxing "Every time I visit the webpage" setting. At least I assumed that was what FIXED! If you want to view the page that is the subject of this go to http://gotweedheads.com


Michael Coyne 6 years ago

Yes That is a good point actually,

# 2 HOURS

Header set Cache-Control "max-age=7200, must-revalidate"

That is the problem with cache - when you make changes it's not always updated immediately unless you specify it - which sort of defeats the point!


psychicdog.net profile image

psychicdog.net 6 years ago Author

Just in case others do not know the max-age is actually seconds. 3600 secs =one hour. Thanks for the contribution Michael - it looks like this directive is a worthwhile speed tip though do you know more about adding "public, must-revalidate" control to the directive. Will new images get missed if the site is being constantly updated if this isn't added?


Michael Coyne 6 years ago

"

Header set Cache-Control "max-age=2592000"

"


michael coyne 6 years ago

you can use a htaccess file with something like this

Header set Cache-Control "max-age=2592000"

As a standard way to cache images. Should improve the javascript loading the images too


psychicdog.net profile image

psychicdog.net 6 years ago Author

I'm purely self-taught and it was just my love and persistence that got me to the point of building respectable pages. Google is a great source of information if you get stuck with anything and there are so many free tutorials out there. The best I found were those by the official body that governs programming standards W3c schools. And by the way, bayareagreatthing - I've 'immortalized' you on my quotes site. Look up your real name using the search box!


bayareagreatthing profile image

bayareagreatthing 6 years ago from Bay Area California

wow- how cool! I am tech challenged but I get the gist of it. I envy you P-dog for knowing this stuff :)


psychicdog.net profile image

psychicdog.net 6 years ago Author

thanks for dropping by Misthaven! Heh it's not so hard to get your head around basic web design and anything you learn can be built on. Watch out though. It can be quite addictive once you start getting creative with programming.Someone once said Programming is Poetry and I think they were right!


MistHaven profile image

MistHaven 6 years ago from New Jersey

Nice. I don't know much about web design per se, but this I have noticed this problem on websites I visit. Thanks for the tip.

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