Develop Reference

fade backgrounds move text up

I have multiple background images that are behind a block of text each. I would like to fade each background image and have the text move up when one background image fades into another.
For example
BG1 (background image 1) has Tegxt1 on top of it. As BG1 fades into BG2, Text1 moves up and is replaced by Text2.
How can I do this with simple jquery and javascript and CSS?
Here's what I tried
this._currentTimeout = setTimeout(function() {
this.slides$.eq(newSlideIndex).css('z-index', 3).fadeTo(ANIMATION_FADE_DURATION, 1, function() {
this.slides$.eq(this.currentSlideIndex).css('z-index', 1).css('opacity', 0);
this.slides$.eq(newSlideIndex).css('z-index', 2);
this.currentSlideIndex = newSlideIndex;
this._setTransitionTimerForNewSlide(this._getNextSlideIndex(), 5000);
}.bind(this));
}.bind(this), durationUntilTransition);

You did not provide enough code to generate a complete working example (How is your html structured? Where is your jQuery located on the page? What does your existing CSS look like?), so unfortunately no one on StackOverflow and give you a perfect answer. The best we can do is create a small demo of what you could do to accomplish this affect. It's then up to you to learn from the example and apply the concept to your own code.
If I was going to try to accomplish this, here's the approach I would take:
Stack images on top of each other with position: absolute;
The first image group should have the highest z-index, so it's on top. CSS can do this!
The second image group should have the second-highest z-index, so that it shows behind the first image during the fade. CSS again!
all other image_groups should have z-index below the second image. Yay for CSS!
Animate the image and text seperately
The image just needs to fade out
The text needs to fade up and out
After the first (top) image group is completely faded, move it to the bottom of the list
Remove the inline style="..." that jQuery's .animate() applies to the image group. Once we do this, the image group will adhere to the css rules we set up in step one.
JS Fiddle Demo
The first step will be done manually by you when you're writing HTML and CSS, but then your jQuery can handle steps 2-4. Then just repeat as much as you'd like. Ask questions if you need to, but try hard to apply this to your own code. Good luck!!

How to detect when all images are loaded and elements are rendered at their appropriate heights

How can I check (with jquery or vanilla js) that all images on a page are loaded, and that they have been rendered at their final, full height, and that their parent elements have adjusted to that height?
I'm implementing a scrollspy function using jquery - something that determines where a user is on a page and highlights their position in a nav, updating their position as they scroll. In order for this to work properly, I need to know the offset.top of each section on the page I want to spy on. If I calculate the offset.top too early, before all images are loaded and displaying at their full height, the offset().top calculation will be incorrect. I want to avoid running the offset().top calculation too many times.
Things i've tried that don't fulfill my needs:
$(document).ready() and $(window).onload() are both too early, as images may not have been rendered at their full height, therefore making the sections not rendered at their full height.
the imagesLoaded library. same problem as above, doesn't account for rendering of images to their full height.

Based on my experience I think it's not trivial. window.onload may help, but it's not reliable when images are loaded dynamically. In the past I was using some kind of hack to make it workable. Basically, I was using window.setInterval and checking if image is really available by looking at property naturalWidth (see: https://developer.mozilla.org/en-US/docs/Web/API/HTMLImageElement).
Here is an example of implementation: https://jsfiddle.net/yu8zr20h/

You are solving this issue in an incorrect way. You need to compare the current Y-value of the users window to the Y-value of all the components, or at least the containers containing the different nav values.
Imagine this is your html-code:
<div id="firstContainer">
<!-- Some content -->
</div>
<div id="secondContainer">
<!-- Some other content -->
</div>
Now you can check the height relative to the complete html page using
document.gelElementBtId('element-id').offsetTop
and the current height of the user using
scrollY
More information using this JSFiddle.

If you have image size metadata (e.g. Rails Active Storage provide it out of the box), you can write height to say dataset:
<img id="image" data-height="700" src="image.jpg" />
Then wait for it to be rendered (watch natural height):
let timer;
let image = document.getElementById("image");
function waitImage() {
if (image.naturalHeight < image.dataset.height) {
timer = setTimeout(function(){
showItems();
}, 300);
} else {
clearTimeout(timer);
useYourFullyRenderedImage();
}
}

Javascript Div Scroll - Some Issues

I copied this from another post, not blindly, I can see what it does but I can't think of a way to fix the problem. I am not really proficient in JavaScript but I can read this snippet.
// The function actually applying the offset
function offsetAnchor() {
if (location.hash.length !== 0) {
window.scrollTo(window.scrollX, window.scrollY - 100);
}
}
// This will capture hash changes while on the page
$(window).on("hashchange", function() {
offsetAnchor();
});
// This is here so that when you enter the page with a hash,
// it can provide the offset in that case too. Having a timeout
// seems necessary to allow the browser to jump to the anchor first.
window.setTimeout(function() {
offsetAnchor();
}, 3);
;(function($) {
$('.swipebox').swipebox();
})(jQuery);
The issue was, that when I was scrolling to DIVs with ID's used for anchor points, I was scrolling slightly too far down as I have a sticky header. I tried using this so when changing DIV it would account for the sticky header, it doesn't exactly work perfectly but the main issue I am having, is that I will have over 12 navigation DIV ids, and every time anyone of them is clicked it no longer goes to the DIV, but instead just scrolls up -100 pixels.
I essentially need a solution that will scroll to just above where I need it without affecting the rest of my menu functionality, it doesn't have to be achieved by JS but that's the only feasible way I can see a solution (I've tried thinking of a CSS only one but margin/padding won't help in this situation of scrolling)
To give one last detail, when clicking on a navigation div it will scroll to that div, and the menu (sticky header) will cover some of the image and the of the item scrolled too. Major problem :)
I can leave a link if you'd like a better description and I am learning JS at the moment, but as this is for a client I'd love to be able to fix it within a timely manner and would greatly appreciate any and all help anyone can offer.
Thank you.

In this question there's an answer for jumping to certain element.
If you want a smooth scroll: look here.

Make images (position:fixed) be visible only inside a DIV

I want to create a website, inspired by http://cirkateater.no/en/ .
The images shall stay at the same position on the Screen (position:fixed), but inside the next div, the second image shall be visible.
My first solution was to use background-images, which worked.
With background-images, it looked like this JSFIDDLE:
http://jsfiddle.net/Ryanous/r7mLm4wg/4/ (i do not own these images)
Consider the following code:
<div class="background" style='background-image:url("http://mintywhite.com/wp-content/uploads/2012/10/fond-ecran-wallpaper-image-arriere-plan-hd-29-HD.jpg");'></div><div class="background" style='background-image:url("http://vpnhotlist.com/wp-content/uploads/2014/03/image.jpg");'></div>
But I also want to move the images via JS later on!
You cant manipulate backgroundimages top-offset easily, so I decided to use an img-tag instead.
Now, using the img-tag, the images seem to be independent of their divs, and overlap each other so that always only one image is visible.
( id like to include my current code but stackoverflow wont let me do. four spaces dont do anything, i cant format my code. )
So my question is:
How can I make images be only visible inside a certain div, but keep their positions fixed?

Putting the style overflow:hidden; on the div would hide all that's outside of the div.

How to keep div focus when the mouse enters a child node

So I have this page here:
http://www.eminentmedia.com/development/powercity/
As you can see when you mouse over the images the div slides up and down to show more information. Unfortunately I have 2 problems that i can't figure out and I've searched but haven't found quite the right answer through google and was hoping someone could point me in the direction of a tutorial.
The first problem is that when you mouse over an image it changes to color (loads a new image), but there's a short delay when the image is loading for the first time so the user sees white. Do I have to preload the images or something in order to fix that?
My second problem is that when you move your mouse over the 'additional content area' it goes crazy and starts going up and down a bunch of times. I just don't have any idea what would cause this but i hope one of you will!
All my code is directly in the source of that page if you would like to view the source.
Thanks in advance for your help!

Yes, you have to preload the images. Thankfully, this is simple:
var images_to_preload = ['myimage.jpg', 'myimage2.jpg', ...];
$.each(images_to_preload, function(i) {
$('<img/>').attr({src: images_to_preload[i]});
});
The other thing you have to understand is that when you use jQuery you have to truly embrace it or you will end up doing things the wrong way. For example, as soon as you find yourself repeating the same piece of code in different places, you are probably doing something wrong. Right now you have this all over the place:
<div id="service" onmouseover="javascript:mouseEnter(this.id);" onmouseout="javascript:mouseLeave(this.id);">
Get that out of your head. Now. Forever. Always. Inline javascript events are not proper, especially when you have a library like jQuery at your disposal. The proper way to do what you want is this:
$(function() {
$('div.box').hover(function() {
$(this).addClass('active');
$(this).find('div.slideup').slideDown('slow');
}, function() {
$(this).removeClass('active');
$(this).find('div.slideup').slideUp('slow');
});
});
(You have to give all the #industrial, #sustainable, etc elements a class of 'box' for the above to work)
These changes will also fix your sliding problem.

I can see your images (the ones that are changing) are set in the background of a div. Here is a jquery script that preloads every image found in a css file. I have had the same problem in the past and this script solves it. It is also very easy to use:
http://www.filamentgroup.com/lab/update_automatically_preload_images_from_css_with_jquery/
I will take a look at your other problem...

1) You should be using the jquery events to drive your mouseovers. Give each div a class to indicate that its a category container and use the hover function to produce the mouseover/mouseout action you're after.
html
<div id="industrial" class="category"></div>
Javascript
$(".category").hover(
function () {
$(this).find('.container').show();
},
function () {
$(this).find('.container').hide();
}
);
I simplified the code to just do show and hide, you'll need to use your additional code to slide up and slide down.
2) Yes, you need to preload your images. Another option would be "sprite" the images. This would involve combining both the black and white and colour versions of each image into a single image. You then set it as the div's background image and simply use CSS to adjust the background-position offset. Essentially, sliding instantly from the black and white to colour images as you rollover. This technique guarentees that both images are fully loaded.