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How to detect scroll inside “body” and get rid of scrollTop() returns 0

I have set a Scroll event to trigger fade out or fade in effect for "$("#btn")" , but I am not even able to detect the scroll event when its is scrolled, when check the value of scroll it return as 0, due to which it is not reflecting anything.
Issue: Not able to detect any kind of scroll event and not able to get scrolled values
Here is the which I tried
https://jsfiddle.net/evwrs0jq/1/
$(document).ready(function(){
$("body").on("scroll", function(){
alert();
var currentScroll = $(this).scrollTop()
var BtnAction = $("#btn");
if (currentScroll > offset) {
BtnAction.fadeOut(duration);
} else {
BtnAction.fadeIn(duration);
}
offset = currentScroll;
});
});

I guess you want this: https://jsfiddle.net/evwrs0jq/2/
<div id="test" ...
$("#test").on("scroll", function(){ ...
The body itself doesn't scroll here, it is the div that scrolls. That's why your alert didn't show up.

Problems with scrollTop animation

I have three divs, each one with some hidden content. When you click on a div, its content is being displayed by sliding down. And at the same time, I'm using scrollTop to make the browser scroll to the top of the block thats been clicked on. The HTML looks like this:
<div class="blocks block1"></div>
<div class="content block1_content"></div>
<div class="blocks block2"></div>
<div class="content block2_content"></div>
<div class="blocks block3"></div>
<div class="content block3_content"></div>
However, im having problems with parts of the scrollTop animation. Here is the JS:
$('.blocks').on("click", function() {
if (!$(this).hasClass('expanded')) {
collapseExpandedFunction();
$('html, body').animate({
scrollTop: $(this).offset().top
}, 500);
$(this).addClass('expanded');
$(this).next().slideDown();
} else if ($(this).hasClass('expanded')) {
collapseExpandedFunction();
}
});
collapseExpandedFunction = function() {
$('.blocks.expanded').removeClass('expanded');
$('.content').slideUp();
};
I made an jsfiddle to easier demonstrate the problem: https://jsfiddle.net/ss53ckyk/3/
Explaination:
If you start toggle the green block and then toggle the red or blue, it's all good. The greens content is being hidden, while the red/blue is displayed and scrolled to the top of the block.
The problem is if you start from the top and moving down. If you first toggle the red one and then either blue or green, the browser won't scroll down correctly.
Another thing i'd like is to make the slideDown happen after the scrollTop animation is done.
Hopefully someone can help me out!
EDIT:
There should only be one blocks content visible at a time. For example, if you click the red once and then the blue, the content of the red should slide up, while the blue is showing.

The asynchronous nature of javascript is causing your issues; namely .slidUp() function. When this event is triggered, it fires an asynchronous event, which is non-blocking to the rest of the function. Therefore, the animate top will take a snapshot of the DOM at a particular moment in time while the .slidUp() function is actioning. Replacing the .slidUp() and .slidDown() with .show() and .hide() to resolve this, but this doesn't provide the responsiveness you require. One thought would be to capture the offsets of each previous content div and use that in the scrollTop function.

EDIT :
Based on the edit, you need to make few adjustments in your code which calculates the scrolltop position based on scrollposition and adding margin based on the corresponding .content div
$(document).ready(function() {
var addMargin = false;
$('.blocks').on("click", function() {
if (!$(this).hasClass('expanded')) {
collapseExpandedFunction();
var doc = document.documentElement;
var ele = this;
var nextEle = $(ele).next();
$(this).addClass('expanded');
var margin = 0;
var scrollTo = 0;
if($(ele).hasClass('expanded'))
{
if(addMargin)
margin = $(nextEle).css('height').replace('px','');
scrollTo = $(ele).offset().top - margin;
}
if(doc.scrollTop != 0 && doc.scrollTop > scrollTo && addMargin)
{
console.log(margin);
scrollTo = scrollTo + 200;
}
$('html, body').animate({
scrollTop: scrollTo
}, 500, function()
{
$(ele).next().slideDown();
});
} else if ($(this).hasClass('expanded')) {
collapseExpandedFunction();
}
});
collapseExpandedFunction = function()
{
$('.blocks.expanded').removeClass('expanded');
$('.content').slideUp();
addMargin = false;
};
window.onscroll = function (e) {
addMargin = true;
}
});
Here's the working code : https://jsfiddle.net/ss53ckyk/13/

How can I set my browser window's scrollbar or a div scrollbar to scroll in increments using animate and scrollTop?

The general idea to the site i am designing is to scroll through a set of menu items horizontally and incrementally underneath a static div that will magnify(increase dimensions and pt size) the contents of a menu items. I don't really need help with the magnify portion because i think it's as simple as adding a mag class to any of the menuItem divs that go underneath the static div. I have been messing with this for a few weeks and the code I have for incrementally scrolling, so far, is this:
$(document).ready(function () {
currentScrollPos = $('#scrollableDiv').scrollTop(120); //sets default scroll pos
/*The incrementScroll function is passed arguments currentScrollPos and UserScroll which are variables that i have initiated earlier in the program, and then initiates a for loop.
-The first statement sets up the variables: nextScrollPos as equal to the currentScrollPos(which by default is 120px) plus 240px(the distance to next menuItem), prevScrollPos as equal to the currentScrollPos(which by default is 120px) minus 240px(the distance to next menuItem).
-The second Statement checks to see if the user has scrolled using var userScroll
-The third statement sets: var CurrentScroll equal to the new scroll position and var userScroll to false*/
function incrementScroll(currentScrollPos, userScroll) {
for (var nextScrollPos = parseInt(currentScrollPos + 240, 10),
prevScrollPos = parseInt(currentScrollPos - 240, 10); //end first statement
userScroll == 'true'; console.log('dude'), //end second statement and begining of third
currentScrollPos = scrollTop(), userScroll = 'false') {
if (scrollTop() < currentScrollPos) {
$('#scrollableDiv').animate({
scrollTop: (parseInt(prevScrollPos, 10))
}, 200);
console.log('scrolln up')
} else if (scrollTop() > currentScrollPos) {
$('#scrollableDiv').animate({
scrollTop: (parseInt(nextScrollPos, 10))
}, 200);
console.log('scrolln down')//fire when
}
}
}
$('#scrollableDiv').scroll(function () {
userScroll = 'true';
_.debounce(incrementScroll, 200); //controls the amount of times the incrementScroll function is called
console.log('straight scrolln')
});
});
I have found a variety of solutions that are nigh close: such as a plugin that snaps to the next or previous div horizontally demo, another solution that also snaps and is based on setTimeout demo, but nothing that nails incrementally scrolling through divs. I also found a way to control the rate at which a user may scroll through the menuItems using debounce which is included in the above code.
The console.logs inside the loop do not fire when I demo the code in jsfiddle which leads me to believe the problem lies within the loop. I'm a noob though so it could be in syntax or anywhere else in the code for that matter. Also in the second demo, i have provided the css for the horizontal static div, but the moment I put it in my html it keeps the js from working.
I would like to write the code instead of using a plugin and any help would be appreciated! Also, thank you ahead of time!

Try this fiddle. Menu container height is 960px to show 4 menu items. "Zoom" div is positioned absolutely at top. When you scroll mouse over this div, menu items shifts to top/bottom. I had to add additional div to bottom to be able to scroll to last 3 menu items. JS code:
jQuery(document).ready(function($){
var current = 0;
var menu = $('.menu-container').scrollTop(0);
var items = menu.find('.menu-item');
var zoom = $('.zoom');
function isVerticalScroll(event){
var e = event.originalEvent;
if (e.axis && e.axis === e.HORIZONTAL_AXIS)
return false;
if (e.wheelDeltaX)
return false;
return true;
}
function handleMouseScroll(event){
if(isVerticalScroll(event)){
var delta = event.originalEvent.wheelDelta * -1 || event.originalEvent.detail;
current += (delta > 0 ? 1 : -1);
if(current < 0)
current = 0;
if(current >= items.length){
current = items.length - 1;
}
menu.stop().animate({
"scrollTop": current * 240
}, 300);
items.removeClass('current').eq(current).addClass('current');
event && event.preventDefault();
return false;
}
}
zoom.on({
"MozMousePixelScroll": handleMouseScroll,
"mousewheel": handleMouseScroll
});
});
Hope it will help.

Update scroll position on resize of window

I'm currently using a combination of smooth scroll and IDs/anchor tags to scroll to content on my site. The code below is getting the ID of the next 'section' in the DOM, and adding it's ID as the 'view next section' href, so once it's clicked, it'll scroll to the top of that div. Then, it iterates through, updating the href with the next ID each time etc until the last section is seen and it scrolls back to the top. Pretty straightforward.
The only problem is that the 'sections' are fullscreen images, so as it's scrolling to the top of the next section, if you resize the browser, the top position of that section (where we scrolled to) has moved, and means the position is lost.
I've created a JSFiddle. You can see this happening after you click the arrow to visit the next section then resize the window: http://jsfiddle.net/WFQ9t/3/
I'm wanting to keep this top position fixed at all times so even if you resize the browser, the scroll position is updated to reflect this.
Thanks in advance,
R
var firstSectionID = $('body .each-section').eq(1).attr('id');
$('.next-section').attr('href', '#' + firstSectionID);
var i = 1;
$('.next-section').click(function() {
var nextSectionID = $('body .each-section').eq(i).attr('id');
i++;
$('.next-section').attr('href', '#' + nextSectionID);
var numberOfSections = $('body .each-section').length;
var lastSectionID = $('body .each-section').eq(numberOfSections).attr('id');
if ($('.next-section').attr('href') == '#' + lastSectionID ) {
$('.next-section').attr('href', '#introduction');
i = 1;
}
});

Ok, Please check out this fiddle: http://jsfiddle.net/WFQ9t/9/
The few things I did were:
Made some global variables to handle the screen number (which screen you're on and also the initial window height. You will use this when the screen loads and also when you click on the .next-session arrow.
var initWinHeight = $(window).height();
var numSection = 0;
Then I tossed those variables into your resizeContent() function
resizeContent(initWinHeight, numSection)
so that it will work on load and resize
I made the body move around where it needs to, to accomodate for the movement of the divs (I still don't understand what divs are moving when the regular animation happens).
$('body').css({
top: (((windowHeight - initWinHeight)*numSection)*-1) + "px"
});
Then in your click function, I add 1 to the section number, reset the initial window height and then also reset the body to top:0. The normal animation you have already puts the next section at the top of the page.
numSection++;
initWinHeight = $(window).height();
$('body').css({top:"0px"}, 1000);
Finally, I reset the numSections counter when you reach the last page (You might have to make this 0 instead of 1)
numSection = 0;
The fiddle has all of this in the correct places, these are just the steps I took to change the code.

Here is a solution that i found, but I dont use anchor links at this point, i use classes
Here is my HTML code:
<section class="section">
Section 1
</section>
<section class="section">
Section 2
</section>
<section class="section">
Section 3
</section>
<section class="section">
Section 4
</section>
And here is my jQuery/Javascript code,
I actually used a preety simple way:
$('.section').first().addClass('active');
/* handle the mousewheel event together with
DOMMouseScroll to work on cross browser */
$(document).on('mousewheel DOMMouseScroll', function (e) {
e.preventDefault();//prevent the default mousewheel scrolling
var active = $('.section.active');
//get the delta to determine the mousewheel scrol UP and DOWN
var delta = e.originalEvent.detail < 0 || e.originalEvent.wheelDelta > 0 ? 1 : -1;
//if the delta value is negative, the user is scrolling down
if (delta < 0) {
next = active.next();
//check if the next section exist and animate the anchoring
if (next.hasClass('section')) {
var timer = setTimeout(function () {
$('body, html').animate({
scrollTop: next.offset().top
}, 800);
next.addClass('active')
.siblings().removeClass('active');
clearTimeout(timer);
}, 200);
}
} else {
prev = active.prev();
if (prev.length) {
var timer = setTimeout(function () {
$('body, html').animate({
scrollTop: prev.offset().top
}, 800);
prev.addClass('active')
.siblings().removeClass('active');
clearTimeout(timer);
}, 200);
}
}
});
/*THE SIMPLE SOLUTION*/
$(window).resize(function(){
var active = $('.section.active')
$('body, html').animate({
scrollTop: active.offset().top
}, 10);
});

Stop Javascript .scrollBottom function

My .scrollBottom button works, but once it auto scrolls to the bottom I can't manually scroll back up because it is active and constantly scrolling down. What does it need for it scroll to absolute bottom and then STOP?
JavaScript
var timeOut;
function scrollToBottom() {
if (document.body.scrollBottom!=0 || document.documentElement.scrollBottom!=0){
window.scrollBy(0,20);
timeOut=setTimeout('scrollToBottom()',10);
}
else clearTimeout(timeOut);
}
HTML
BUTTON

I found that by removing the timeOut=setTimeout('scrollToBottom()',10);
the button scrolls down by 20 pixels on press.
With that information - I changed the window.scrollBy(0,20); to a ridiculous number like: window.scrollBy(0,2000000);
so I got this code:
var timeOut;
function scrollToBottom() {
document.body.scrollBottom!=0 || document.documentElement.scrollBottom!=0
window.scrollBy(0,2000000);
}
And paired with
html {
scroll-behavior: smooth;
}
It does the trick :)