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Removing and adding a class through javascript smoothly

I am trying to create this animation where the title is visible in the page initially then when you scroll down you trigger the title to slowly fade away and a subtitle fades in right after. I have the title part working but I can't seem to get the subtitle to appear with a smooth transition. At first I have my subtitle at "visibility:hidden" then when I scroll and the javascript adds the transition in class, it just abruptly comes in disregarding the transition property I gave it. Here is the fiddler I set up. Below is the javascript and css (respectively) i'm using to get this animation to work. Of course if there area any easier ways to achieve this feel free to let me know. Any advice or help will be GREATLY appreciated I have been researching and trying things to no avail.
Javascript
const element = document.getElementById('title');
const element2 = document.getElementById('subtitle');
window.onscroll = function() {
console.log("document element");
console.log(document.documentElement.scrollTop);
console.log("scrolling elemnent");
if (window.scrollY > 0) {
element.classList.add('fadeout');
element2.classList.add('fadein');
console.log("hello");
}
}
.fadeout {
visibility: hidden;
opacity: 0;
transition: visibility 0s 2s, opacity 2s linear;
}
.two {
visibility: hidden;
}
#subtitle {
transition: opacity 2s linear;
}
.fadein {
visibility: visible;
opacity: 1;
transition: opacity 2s linear;
}

Currently your subtitle is at full opacity when you are fading it in (Because the visibility property does not set the opacity it just makes the element invisible)
Add opacity:0; to the .two CSS so that it will fade in.
Updated fiddle https://jsfiddle.net/s2cban6q (line 32 of CSS changed)

jQuery mouseenter and mouseleave fadeTo prevent delayed repeat

So, I've got a div which fades up on mouse enter and down on mouseleave which works fine.
$('.myDiv').mouseenter(function(){
$(this).fadeTo('slow', 1);
});
$('.myDiv').mouseleave(function(){
$(this).fadeTo('slow', 0.4);
});
See jsfiddle .
However, if you quickly move the mouse over and back and again several times, the div will "flash" as the animation keeps running. Is there a way to stop this from occurring?
I've tried callbacks but haven't got the desired effect.
Any suggestions?

Try:
$('.myDiv').mouseenter(function(){
$(this).stop();
$(this).fadeTo('slow', 1);
});
$('.myDiv').mouseleave(function(){
$(this).stop();
$(this).fadeTo('slow', 0.4);
});
https://jsfiddle.net/1Lrcubwp/

A better way is to use CSS.
Javascript shouldn't be used for this kind of animation as it will make your website slow.
See my example below.
.fade {
background-color: red;
width: 200px;
height: 200px;
opacity: 0.4;
filter: alpha(opacity=40); /* For IE8 and earlier */
transition: opacity .25s ease-in-out;
-moz-transition: opacity .25s ease-in-out;
-webkit-transition: opacity .25s ease-in-out;
cursor: pointer;
}
.fade:hover {
opacity: 1;
}
<div class='fade'></div>

How can I highlight a specific div from a hash in the URL?

When a user comes to a website via www.example.com/#div4, I would like the division specified in the URL to be highlighted with #F37736 (orange) and then within 2 seconds transition smoothly back to #00A087 (the default color).
The div to be highlighted as a class of "fixed-nav-bar".
What I've tried:
var hash = false;
checkHash();
function checkHash(){
if(window.location.hash != hash) {
hash = window.location.hash;
} t=setTimeout("checkHash()",400);
};

You could look for the hash, then target the division by it's class name. You'll immediately change the color of the div to your orange color, then animate it back to your default color.
You will need to include the jQuery Color library to animate the background-color though, as vanilla jQuery cannot animate background-color. You can also use jQuery UI's highlight effect, thought the UI library is a little heavier in size.
$(document).ready(function () {
var hash = window.location.hash;
$('.' + hash).css('background-color', '#F37736').animate({
backgroundColor: '#00A087'
}, 2000);
});

This can be solved with just CSS using the :target pseudo-class. It allows you to highlight the item that has an ID matching the hash in your URL. A very simple example of this would be:
div {
background-color: #00A087;
}
div:target {
background-color: #F37736;
}
By default, a div would have a default colour but on finding a match it would switch to something different. To make it work in the way you specified, just sprinkle a bit of animation magic:
div {
background-color: #00A087;
}
div:target {
background-color: #F37736;
animation-delay: 2s;
animation-fill-mode: forwards;
animation-duration: 4s;
animation-name: highlight;
animation-timing-function: ease-in-out;
}
#keyframes highlight {
from {
background-color: #F37736;
}
to {
background-color: #00A087;
}
}
Here I've set the animation to delay for 2 seconds and to maintain the final state of the animation.
With the various properties available you can mix and match to make it work a little differently but this would achieve what was being asked in the question.
Example on CodePen

I'm assuming that, you wanna highlight the background color on some events.
Try adding this css to your code. This will highlight background color on hover.
.fixed-nav-bar {
background-color: #f37736;
}
.fixed-nav-bar:hover {
background-color: #00a087;
-webkit-transition: background-color 2000ms linear;
-moz-transition: background-color 2000ms linear;
-o-transition: background-color 2000ms linear;
-ms-transition: background-color 2000ms linear;
transition: background-color 2000ms linear;
}
Hope this will help you.

jquery background color fade in on scroll

I want the background of the header to fade in after a number of pixel scrolled. With the code below i kinda get it but not much right! Any idea? thanks!
$(function () {
$(window).scroll(function () {
$(document).scrollTop() > 100 ? $('header').css({
"background": 1
}).fadeIn() : $('header').css({
"background": 0
}).fadeOut();
});
})

A combination of Miquel Las Heras and Owen 'Coves' Jones's answers, who both submitted a not completely on-topic or not complete answer.
Use background trasitions (CSS3) and jQuery simultaneously.
JSFiddle
jQuery
$(document).ready(function () {
$(window).scroll(function () {
if ($(document).scrollTop() > 100) {
$("header").addClass("scrolled");
} else {
$("header").removeClass("scrolled");
}
});
});
CSS
header {
background-color:blue;
-webkit-transition: background-color 700ms linear;
-moz-transition: background-color 700ms linear;
-o-transition: background-color 700ms linear;
-ms-transition: background-color 700ms linear;
transition: background-color 700ms linear;
}
header.scrolled {
background-color: red;
}
Update February 3rd, 2017
browser support is very good, and the less performing jQuery solution below should not be used. Browser support.
Cross-browser solution
If you want to make it more cross-browser compatible, you can try the color plugin. But from what I've tested, it has quite a bad performance.
JSFiddle
$(document).ready(function () {
$(window).scroll(function () {
if ($(document).scrollTop() > 100) {
$("header").animate({
backgroundColor: "red"
}, 200);
} else {
$("header").animate({
backgroundColor: "blue"
}, 200);
}
});
});
Don't forget the plugin itself:
//cdnjs.cloudflare.com/ajax/libs/jquery-color/2.1.2/jquery.color.js

First, as was mentioned in the other answer, you will need to include jQuery UI or the jQuery Color plugin for color animation.
Second, and this is just winging it, but give this the old college try:
$(function(){
$(window).scroll(function(){
var $scrollPercent = ($(document).scrollTop() / 100);
if($scrollPercent <= 1){
$('header').css({backgroundColor:'rgba(0,0,0,'+$scrollPercent+')'});
}
});
});
This should give you a gradual fade in based on the amount down the page you scroll. This means that if you scroll 50 px down, your background color opacity would be set to 50% (50 px down / 100 px height wanted). You can also easily change the amount of height that you want to scroll down to reach full opacity very easily this way.
EDIT So it turns out you just want to fade in the color after 100px ... not my gradual fade in. No problem.
Others have pointed out the wonderful (and much better) CSS3 way to do it ... create a transition effect, and add a class on scroll. I won't steal their thunder, but I shall provide an alternative that works back to ancient browsers too.
Add an additional line of HTML inside of your header at the top:
<div class="header">
<div class="headerBackground"></div>
<!-- other header stuffs -->
</div>
Then set its CSS as such:
.header {
position:relative;
}
.headerBackground {
position:absolute;
top:0;
left:0;
right:0;
bottom:0;
background-color:rgb(0,0,0);
opacity:0;
filter:alpha(opacity=0); // for IE8 and below
}
Then use the following jQuery:
$(function(){
$(window).scroll(function(){
var $bg = $('.headerBackground');
if($(document).scrollTop() >= 100){
$bg.animate({opacity:1},500); // or whatever speed you want
} else {
$bg.animate({opacity:0},500);
}
});
});
This also has the added benefit of not requiring another library (jQuery UI / jQuery Color plugin). The downside is, of course, the non-semantic HTML. Like I said, just another alternative.

I prefer to create 2 css classes for this type of issues. One for when window is scrolled and one for when it's not:
header { background: transparent; }
header.scrolled { background: #f2f2f2; }
Then the javascript should be:
$(function () {
$(window).scroll(function () {
if($(document).scrollTop()>100){
$('header').addClass('scrolled');
}
else {
$('header').removeClass('scrolled');
}
});
})

your code is correct, but jQuery does not natively support color animation. you need a plugin or jquery-ui for that: http://jqueryui.com/animate/
EDIT: actually, your code is kinda wrong. you want to set the backgroundColor to something. background: 1 is invalid css:
so .css({'backgroundColor': 'red'}) and then .css({'backgroundColor': 'blue'})

If you don't need to support a lot of older browsers you can animate background colours with a combination of jQuery and css3 transitions:
Take the HTML:
<div id="myBox">Stuff here</div>
And the javascript:
var myBox = $('#myBox');
myBox.on('click', function (el) {
myBox.css('background-color', 'red');
}
Then click the element #myBox will change its background colour red. Instantly, with no fade.
If you also put in place the css code:
#myBox {
-webkit-transition: background-color 300ms ease-in-out;
-moz-transition: background-color 300ms ease-in-out;
transition: background-color 300ms ease-in-out;
}
Then any colour changes to the background will be faded over 300ms. Works on all latest version browsers, but not on IE 9 and below.

The solution that I ended up using is as follows:
I created a section that I'm fading in and out based on the scroll position.
CSS
.backTex {
width:100%;
height:500px;
margin-top:50px;
background-color: #myGreen;
//Height
transition: height 0.5s ease;
-webkit-transition: height 0.5s ease;
-moz-transition: height 0.5s ease;
-o-transition: height 0.5s ease;
-ms-transition: height 0.5s ease;
//Background-Color
transition: background-color 0.5s ease;
-webkit-transition: background-color 0.5s ease;
-moz-transition: background-color 0.5s ease;
-o-transition: background-color 0.5s ease;
-ms-transition: background-color 0.5s ease;
transition: background-color 0.5s ease;
}
jQuery
$(document).scroll(function() {
var positionScroll = $(this).scrollTop();
if(positionScroll <= 499) {
$(".backTex").css("background-color", "#fff");
} else if (positionScroll > 500 && positionScroll < 1100) {
$(".backTex").css("background-color", "#2ecc71");
} else {
$(".backTex").css("background-color", "#fff");
}
});
As far as compatibility, I haven't noticed any issues between browsers as of yet. Please reply to my post if you experience any. Thanks!

confusion regarding toggle() effect and event in jquery

I have two div elements "trigger" and "target". I was looking for a mechanism where every time "trigger" is clicked, a script animates the height of "target". However I need it to toggle between 0px and 100px. After some research I found this
On searching a little I found the following script
$("#trigger").toggle(function(){
$("#target").animate({height:40},200);
},function(){
$("#target").animate({height:10},200);
});
However it didnt seem to work.. after some more searching I came across the following script
$(document).ready(function()
{$("#trigger").click(function()
{
$('#target').toggle(
function()
{
$('#target').animate({height: "250"}, 1500);
},
function()
{
$('#target').animate({height: "0"}, 1500);
});
});
});
and this didn't work either. The element does animate but along with the height, the width and opacity would also animate. Further research brought me to this effect. So basically there are two toggle(). in jquery, and i'm confused about how each is used. All I want to do is animate the height of one element with a toggle when another element is clicked. I hope I have been clear enough.

You could just add a variable like var trigger = false;
var trigger = false;
$("#trigger").click(function(){
if(!trigger) {
$("#target").animate({height:40},200);
trigger = true;
}
else {
$("#target").animate({height:10},200);
trigger = false;
}
});

You could use toggleClass instead:
$("#trigger").click(function() {
$(".target").toggleClass("higher");
});
in your css you then use:
.target {
height:50px;
background-color:#f00;
-webkit-transition: height 1s;
-moz-transition: height 1s;
-ms-transition: height 1s;
-o-transition: height 1s;
transition: height 1s;
}
.higher {
height:100px;
}
http://jsfiddle.net/JSfa3/