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FadeIn animation using CSS3 in Javascript

As jQuery.fadeIn is not very smooth on mobile devices I try to use CSS but it doesn't work as expected. How to create a smooth CSS animation using Javascript?
In general this is what I'm trying:
$('div')
.css('opacity', 0) // at first, set it transparent
.css('display', 'block') // make it appear
.css('transition', 'opacity 1000ms linear') // set a transition
.css('opacity', 1); // let it fade in
https://jsfiddle.net/8xa89y04/
EDIT1:
I'm not searching a solution using static CSS classes. The point is: I need to set this dynamically in Javascript code - a replacement for jQuerys fadeIn() for example.

Your logic isn't quite right. Firstly you cannot animate display, so to achieve what you require the element has to always be rendered in the DOM (ie. anything but display: none). Secondly, the transition property should be placed within the CSS styling itself. Finally you can make this much more simple by setting all the rules in CSS classes and just turning the class on/off. Try this:
div {
position: absolute;
width: 100px;
height: 100px;
background-color: black;
opacity: 0;
transition: opacity 1000ms linear;
}
.foo {
opacity: 1;
}
$('div').addClass('foo');
Working example

Use this code.
CSS
div {
width: 100px;
height: 100px;
background-color: black;
transition:opacity 2s;
}
JavaScript
$('div').hover(function(){
$(this).css('opacity','0');
})

Without using CSS properly, you are going the long way about it. You'll need to emulate what you would normally do in CSS, using JavaScript, so you'll be setting all your CSS properties, transitions etc, then applying them with js.
I can't personally see any benefit in doing this. Using actual CSS would be cleaner, more efficient, more maintainable, and simply a plain better solution to what you need.

I think this is what you are looking for.
$('div').css({"display":"block", "opacity":"0"}) //Make div visible and opacity as "0"
$('div').animate({opacity :1}, 1000); //Animate div to opacity "1"
Take a look at this Demo

Found the cause here: CSS transitions do not work when assigned trough JavaScript
To give this attention I need to give the browser some time - or better: a working slot to activate the transition as the time seems not to be a problem.
The following code cuts the process in two by using setTimeout()... and it works!
var div = $('div');
// first process
div
.css('opacity', 0) // initial opacity
.css('display', 'block') // make it appear (but still transparent)
.css('transition', 'opacity 1s linear'); // set up a transition for opacity
// break - start the transition in a new "thread" by using setTimeout()
window.setTimeout(function(){
div.css('opacity', 1); // start fade in
}, 1); // on my desktop browser only 1ms is enough but this
// may depend on the device performance
// maybe we need a bigger timeout on mobile devices

Angular JS and Animate.css: fade animation is janky

I have a dialog in which I'd like to display one of two things depending on the state of a variable. So, I hooked up 2 versions of a form with ng-if.
When you click "delete" button on first state, it toggles to the second state.
I wanted to make it less abrupt, so I tried adding some css:
[ng-if].ng-enter {
animation: fadeIn .5s;
}
[ng-if].ng-leave {
animation: fadeOut .5s;
}
These animations come from the bower package "animate css":
#keyframes fadeIn {
0% {opacity: 0;}
100% {opacity: 1;}
}
.fadeIn {
animation-name: fadeIn;
}
However, as you can see in my animated GIF below, what happens is that for a second BOTH forms appear, making the dialog taller, then one fades out.
Is there no way to do a simple fadein/fadeout as in jQuery? I used to do this all the time with it, but trying to get nice UI animation in Angular is eluding me.

I had a similar problem with an Angular app and animations. I ended up having to use jquery - I wish I had a better answer - but it turned out beautifully. One note, though, I had to wrap any jquery I used in a noConflict() and use body on click plus the element because it doesn't exist yet in the DOM:
$.noConflict();jQuery( document ).ready(function( $ ) {
$('body').on('click', "#toggler", function(){
$('#div_to_show').slideDown();
});
});
I realize this a tangential answer and not an elegant solution but it worked for me to get it out the door under a tight deadline.

A clean solution is to change the state you use to check which form is to display when the animation ng-leave ends.
You can use a second variable to set the ng-leave class in the form that will be hidden.
I can't post you some code because i don't know your js and html.

css3 transition on background image doesn't work in Firefox

This is a follow up to my question here: jquery UI add class with animation does't work
See the new jsfiddle and try this in Firefox: http://jsfiddle.net/40mga4vy/3/
-webkit-transition: all 2.0s ease;
-moz-transition: all 2.0s ease;
-o-transition: all 2.0s ease;
transition: all 2.0s ease;
This code in combination with some jquery animates a background image change when selecting a new background image from a select-element. It works in all browsers except Firefox (tested in MacOS 35.0.1).
While animating a change in the background color and width/height properties works like a charme in FF: http://jsfiddle.net/tw16/JfK6N/ - animating a background image does not work.
Researching showed that a "left" property has to be set but it turned out to not have any impact. I also tried various notations but with no success, I cannot make it work.
There is a workaround shown in this fiddle:
http://jsfiddle.net/40mga4vy/1/
function changeBackground() {
$('#wallpaper').removeClass();
$("#wallpaper").addClass("wallpaper_" + $("#select_category").val()).css('opacity','0').animate({opacity:'1'});
};
This works in FF but its a bit ugly as the class is removed and then opacity raises afterwards (doesn't look as smooth as the css solution).
Any hints/tricks or is this simply not supported?

As far as I know, there is no suport in any browser to swap images smoothly in one single element in css.
After you do what you need, make sure you take a look into performance, your workaround is not as much as efficient as it could. In this code
$("#wallpaper").addClass("wallpaper_" + $("#select_category").val()).css('opacity','0').animate({opacity:'1'});,
the browser will take every single step until
.animate({opacity:'1'}).
For instance, the browser first has to find $("#wallpaper") then, it will call for .addClass("wallpaper_" + ...);
and concatenate the result from finding $("#select_category") then getting .val() and so on. everytime this function is called, it will iterate through every single of these objects, so it is not as efficient as probably could and with two more animations in the page, it may became a bit laggy, if possible, use animations through CSS.
Anyway, what I sugest you to do is (if i'm right about what you want), just do what's in here https://jsfiddle.net/bmjg5g9s/

How to correctly wait until JavaScript applies inline Css

I have this jsFiddle. When the button is clicked, I want to put the red div behind the black one immediately, then start the animation.
var red = document.getElementById("red");
var button = document.getElementById("button");
button.addEventListener("click",function () {
red.style.zIndex = -1;
red.classList.remove("shifted");
});
However, as you can see, they seem to be occurring as two separate actions. I know I can use setTimeout to wait until the zIndex property is applied, but I do not know how long I am supposed to wait, and the duration perhaps differs from browsers to computers.
Should I create a loop that will check if zindex was applied? But this also sounds like an unintelligent solution. What is the correct way?
EDIT: I do not want to change the zIndex on the black div.

You can bind to the transitioned state of the element, something like this:
("#mySelector").bind("transitionend", function(){ 'yourcodehere' });
Also, here is some info on it:
https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Using_CSS_transitions
https://developer.mozilla.org/en-US/docs/Web/Reference/Events/transitionend
Without jQuery:
el.addEventListener("transitionend", updateTransition, true);
Edit:
There was some confusion as to the usage of:
-webkit-transition-duration: 1s;
This is applied like a styling as well. So anytime you make alterations to the element it is on, you are triggering this. You have TWO transition calls, one for setting the z-index, another for the movement.

Just put a
-webkit-transition-property: -webkit-transform;
into the #red and everything is fine. ;) This applies the transition only to specified property.
JSFIDDLE: http://jsfiddle.net/Qvh7G/.

The problem is with zIndex - the transform time delays the change in the zIndex.
You can simply force the duration for the transform property.
Replace:
-webkit-transition-duration: 1s;
With
-webkit-transition: -webkit-transform 1s; // ease-in;

Does jQuery animate between two different CSS classes?

I am trying to understand how jQuery animations work.
For instance, if I have an a element with CSS that makes it look like a clickable image and a given with and height in CSS, how would I safely animate the width and height of this element?
Do I need to animate the values in the CSS class? Or do I need to set a new CSS class with the target values for width and height, and let jQuery animate from oldClass to newClass?
Or can I simply use the .width() and .height() methods of jQuery, regardless of what values are specified in CSS?
What confuses me is: If I tweak the width of an element with jQuery, does this also modify my CSS, or does jQuery / JavaScript simply override the specified values in CSS with something else? I mean: After use jQuery to edit the width, does this width become the new value in the CSS file as well? Can I apply this class to other elements and they will have the new width?

It will overide inline style.
I will now show a version with top, left being animated but you can apply it on almost all CSS properties.
HTML
<span id="test">blablabla</span>
CSS
span{
position:absolute;
display:block;
height:50px;
width:50px;
}
jquery
$('#test').animate({top:'100px',left:'50px'}, 500);
fiddle

I know it's been a long time, but it may help someone looking for the answer anyway. Relying on CSS3 transition property can lead to trouble when wanting to support older browsers.
The requested behaviour of animating between two states (CSS Classes) can fully be accomplished by using jQuery UI, which supports this by extending the switchClass() method. It also supports all the perks of the animate() method, such as duration, easing, callback, etc.
As the official documentation states: '
Similar to native CSS transitions, jQuery UI's class animations
provide a smooth transition from one state to another while allowing
you to keep all the details about which styles to change in CSS and
out of your JavaScript.
You can read all about it here.
jQuery UI can also be compiled to include only the things you need, so you can reduce the size of the library by excluding the features you won't use. Check the available options here.
Hope it helped someone!

jQuery animate only animates numeric css values. It will not animate between classes (see example below for how to do that). The .animate() function adds the css you give it as a paramater and adds it as inline css. It will always override your stylesheet css. This is fine but a little messy and can get out of control very easily.
However, if you want to animate between classes, it is better for performance and cleaner to use css3 transition property. See example:
HTML
<div class="myTestAnimation">Something to test</div>
JQuery (could use vanilla javascript for this as well). Just toggling between classes. This way you don't have any styling info in your css at all.
jQuery(document).ready(function($) {
$(".myTestAnimation").click(function() {
$(this).toggleClass("animate");
});
});
CSS (this animates the width and height and background color) .animate() will not animate background color so that is an added bonus.
.myTestAnimation {
width: 50px;
height: 50px;
background-color: red;
-webkit-transition: background-color 300ms linear, width 300ms linear, height 300ms linear;
transition: background-color 300ms linear, width 300ms linear, height 300ms linear;
position: relative;
}
.myTestAnimation.animate {
background-color: blue;
width: 200px;
height: 200px;
}