Develop Reference

CSS/JavaScript - Scroll snap when user starts scrolling

I recently found this website that uses scroll snapping. I looked into it and found that CSS supports this. However, it looks like snapping happens after the user stops scrolling. The same applies with the answer to this question.
The next thing I tried was using window.scrollTo and react-scroll, but both of these weren't as smooth as the website I've linked as an example since the user could still "fight" the scrolling by scrolling in the other direction.
I want it to scroll snap when the user starts scrolling. How can I do this with CSS or JavaScript?

The developer you were looking at is using this js script if you ant to emulate it exactly https://alvarotrigo.com/fullPage/

If jQuery is an option, that would be the easiest solution with the best browser compatibility. You can use the "wheel" event listener to detect the direction of the scroll, and then use jQuery animate to scroll the window to the appropriate element. I've provided an example based on this GitHub repo: https://github.com/epranka/sections-slider.
(function($) {
var selector = ".section";
var direction;
var $slide;
var offsetTop;
var $slides = $(selector);
var currentSlide = 0;
var isAnimating = false;
var stopAnimation = function() {
setTimeout(function() {
isAnimating = false;
}, 300);
};
var bottomIsReached = function($elem) {
var rect = $elem[0].getBoundingClientRect();
return rect.bottom <= $(window).height();
};
var topIsReached = function($elem) {
var rect = $elem[0].getBoundingClientRect();
return rect.top >= 0;
};
document.addEventListener(
"wheel",
function(event) {
var $currentSlide = $($slides[currentSlide]);
if (isAnimating) {
event.preventDefault();
return;
}
direction = -event.deltaY;
if (direction < 0) {
// next
if (currentSlide + 1 >= $slides.length) {
return;
}
if (!bottomIsReached($currentSlide)) {
return;
}
event.preventDefault();
currentSlide++;
$slide = $($slides[currentSlide]);
offsetTop = $slide.offset().top;
isAnimating = true;
$("html, body").animate({
scrollTop: offsetTop
},
1000,
stopAnimation
);
} else {
// back
if (currentSlide - 1 < 0) {
return;
}
if (!topIsReached($currentSlide)) {
return;
}
event.preventDefault();
currentSlide--;
$slide = $($slides[currentSlide]);
offsetTop = $slide.offset().top;
isAnimating = true;
$("html, body").animate({
scrollTop: offsetTop
},
1000,
stopAnimation
);
}
}, {
passive: false
}
);
})(jQuery);
.section {
position: relative;
display: flex;
height: 100vh;
}
#section1 {
background: blue;
}
#section2 {
background: #ff8c42;
}
#section3 {
background: #6699cc;
}
#section4 {
background: #00b9ae;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div id="section1" class="section"></div>
<div id="section2" class="section"></div>
<div id="section3" class="section"></div>
<div id="section4" class="section"></div>

Check when element appears in the viewport -> addClass

I have a lot of objects in the dom tree, on which i'm adding new class, when they appeat in the viewport. But my code is very slow - it causes page to slow down...
I have such dom:
...
<span class="animation"></span>
...
and such jquery:
$.each($('.animation'), function() {
$(this).data('offset-top', Math.round($(this).offset().top));
});
var wH = $(window).height();
$(window).on('scroll resize load touchmove', function () {
var windowScroll = $(this).scrollTop();
$.each($('.animation'), function() {
if (windowScroll > (($(this).data('offset-top') + 200) - wH)){
$(this).addClass('isShownClass');
}
});
});
maybe i can somehow speed up my scroll checking and class applying?

You can use the Intersection Observer API to detect when an element appears in the viewport. Here is an example that adds a class to an element that is scrolled into the viewport and animates the background color from red to blue:
var targetElement = document.querySelector('.block');
var observer = new IntersectionObserver(onChange);
observer.observe(targetElement);
function onChange(entries) {
entries.forEach(function (entry) {
entry.target.classList.add('in-viewport');
observer.unobserve(entry.target);
});
}
body {
margin: 0;
height: 9000px;
}
.block {
width: 100%;
height: 200px;
margin-top: 2000px;
background-color: red;
transition: background 1s linear;
}
.block.in-viewport {
background-color: blue;
}
<div class="block">
</div>

The Intersection Observer API method works on chrome only, but the performance faster by 100%. The code below loads in 3/1000 second
$(document).ready(function () {
'use strict';
var startTime, endTime, sum;
startTime = Date.now();
var anim = $('.animation');
anim.each(function (index, elem) {
var animoffset = $(elem).offset().top;
$(window).on('scroll resize touchmove', function() {
var winScTop = $(this).scrollTop();
var windowHeight = $(window).height();
var winBottom = winScTop + windowHeight;
if ( winBottom >= animoffset ) {
$(elem).addClass('showed');
}
});
});
endTime = Date.now();
sum = endTime - startTime;
console.log('loaded in: '+sum);
});
html {
height: 100%;
}
body {
margin: 0;
height: 9000px;
}
.animation {
display: block;
width: 400px;
height: 400px;
background-color: blue;
margin-top: 1000px;
}
.animation:not(:first-of-type) {
margin-top: 10px;
}
.animation.showed {
background-color: yellow;
transition: all 3s ease
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.10.1/jquery.min.js"></script>
<span class="animation"></span>
<span class="animation"></span>
<span class="animation"></span>
<span class="animation"></span>

IntersectionObserver has a limited support in browsers, but it's improving.
I'm basically lazy loading the polyfill only if the browser user is loading my website in doesn't support IntersectionObserver API with the code bellow.
loadPolyfills()
.then(() => /* Render React application now that your Polyfills are
ready */)
/**
* Do feature detection, to figure out which polyfills needs to be imported.
**/
function loadPolyfills() {
const polyfills = []
if (!supportsIntersectionObserver()) {
polyfills.push(import('intersection-observer'))
}
return Promise.all(polyfills)
}
function supportsIntersectionObserver() {
return (
'IntersectionObserver' in global &&
'IntersectionObserverEntry' in global &&
'intersectionRatio' in IntersectionObserverEntry.prototype
)
}

How do I fix a div during scroll relative to Squarespace image blocks?

I'm trying to fade in/out and fix the blue div on the left when scrolled relative to the image blocks on the right.
http://www.warface.co.uk/#/testing/
pass: squared
.meta { /*This is the block I'm trying to stick/*
background: blue;
position: fixed;
width: 372px;
float: left;
z-index: 3;
right: 100%;
}

Here is the basics in JavaScript:
function controlMeta() {
var meta = document.querySelector("div.meta");
console.log(meta);
if (window.scrollY > 500) {
meta.style.display = "none";
} else {
meta.style.display = "block";
}
}
window.addEventListener("scroll", function () {
controlMeta();
})
You can get your elements scroll position with something like this:
document.getElementById("57513a9220c6475fb77061c5").getBoundingClientRect().top+window.scrollY
EDIT 1
Here is a method for associating elements with the meta box, based upon the previous:
//Load elements that affect the meta box
var meta = [];
var images = document.querySelector('.sqs-gallery').getElementsByTagName('img');
for (var i = 0; i < images.length; i++) {
meta.push({
node : images[i],
height : images[i].height,
//top is used with scroll position to determine which element we are looking at
top : images[i].getBoundingClientRect().top + window.scrollY
});
}
function controlMeta() {
meta.filter(function (el) {
//You might need to pad your filter a little
return window.scrollY < el.top && window.scrollY > el.top - el.height;
}).forEach(function (el) {
//These are the matching elements. I'm just fetching the src as an example
document.querySelector("div.meta div.body").innerHTML = el.node.src;
});
}
window.addEventListener("scroll", function () {
controlMeta();
});

Animate/Ease an element to position when other elements disappear

Please take a look at this fiddle: http://jsfiddle.net/dhcyA/
Try clicking on a block. What I want is that when the other elements disapear, the selected block will animate/ease to his giving position instead of just jumping like it does now. Then the same animation repeats itself when clicking again on the box, but then back to place.
Maybe to keep in mind:
I'm using a reponsive design, which means those blocks can be vertical and horizontal after scaling the window.
Any redevisions on the fiddle or suggustions would be great!

Here is my solution.
On your existing markup, I added a wrapper division to calculate the position of boxes inside the wrapper. Like this
<div id="wrapper">
<div class="block">
<h2>I'm block 1</h2>
</div>
....
</div>
To maintain the fluidness of the block, I created a function to position the block on the wrapper. Here is the function for position of the blocks:
var reposition = function() {
wrapper = $("#wrapper");
console.log(wrapper.innerWidth());
pLeft = 0;
pTop = 0;
maxRowHeight = 0;
$(".block").each(function(){
if($(this).data('active')) {
$(this).data('top', pTop);
$(this).data('left', pLeft);
} else {
$(this).stop(0,0).animate({
'top' : pTop + 'px',
'left' : pLeft + 'px'
});
}
pLeft += $(this).outerWidth() + parseInt($(this).css('marginLeft'));
if($(this).height() > maxRowHeight) maxRowHeight = $(this).outerHeight() + parseInt($(this).css('marginTop')); //Find out the longest block on the row
if(pLeft + $(this).next().outerWidth() + parseInt($(this).next().css('marginLeft')) >= wrapper.innerWidth()) {
pLeft = 0;
pTop += maxRowHeight;
maxRowHeight = 0;
}
});
};
Finally, the script to toggle the block
$(".block").click(function() {
$(this).siblings().slideToggle('slow'); //Toggle other blocks
if(!$(this).data('active')){ //if the block is not active
$(this).data('left', $(this).position().left); //sets its left
$(this).data('top', $(this).position().top); // and top position
$(this).animate({ //animate at the top and bottom
top:0,
left:0
},'slow');
$(this).data('active',true);
}else{
$(this).animate({ //animate to its last known position
top:$(this).data('top'),
left:$(this).data('left')
},'slow');
$(this).data('active',false);
}
});
Demos
Demo[Full] (Resize this to see the fluidness maintained)
Demo[Full] (version showing variable heights)
Here is what this solutions gives:
Remembers the last position and gradually animate to/from this position
Block positions are calculated and animated on load and every resize
Repositioning happens on $(window).resize() thus maintaining the fluid nature of the block, despite the use of position absolute
Support variable heights
Minor change on existing markup & CSS
Also fixed two issues extended by Gaby
Accounts for each block margin independently
Recalculates the position of the element after resize

Final Update
Here is a full working solution (pretty straight forward in my opinion) with JS to set the positioning (a simple calculation) and CSS transitions for the rest..
Demo at http://jsfiddle.net/gaby/pYdKB/3/
It maintains the fluidity of float:left and works with any number of elements, and you can keep the :nth-child for the styling, and it will also work if you want to leave more than one element visible..
javascript
var wrapper = $('.wrapper'),
boxes = wrapper.children(),
boxWidth = boxes.first().outerWidth(true),
boxHeight = boxes.first().outerHeight(true);
function rePosition(){
var w = wrapper.width(),
breakat = Math.floor( w / boxWidth ); // calculate fluid layout, just like float:left
boxes
.filter(':not(.go)')
.each(function(i){
var matrixX = ((i)%breakat)+1,
matrixY = Math.ceil((i+1)/breakat);
$(this).css({
left:(matrixX-1) * boxWidth ,
top: (matrixY-1) * boxHeight
});
});
}
$('.box').click(function(){
$(this)
.siblings()
.toggleClass('go');// just add the go class, and let CSS handle the rest
rePosition(); // recalculate final positions and let CSS animate the boxes
});
$(window).resize(rePosition);
$(window).trigger('resize');
CSS
.wrapper{
position:relative;
}
.box{
width:200px;
height:100px;
position:absolute;
margin:5px;
cursor:pointer;
overflow:hidden;
text-align: center;
line-height: 100px;
-moz-transition-property: top,left,width,height;
-webkit-transition-property: top,left,width,height;
-ms-transition-property: top,left,width,height;
-o-transition-property: top,left,width,height;
transition-property: top,left,width,height;
-moz-transition-duration: 1s;
-webkit-transition-duration: 1s;
-ms-transition-duration: 1s;
-o-transition-duration: 1s;
transition-duration: 1s;
}
.go{
height:0;
width:0;
}
note: As #Athari correctly mentioned in the comments, you should include all browser prefixes for the widest support. (my initial answer only included moz / webkit and the standard)
Original Answer
You can not do it directly with your current HTML structure. The floated concept does not support it.
But if you can afford an extra wrapper, then it is no problem..
Just slide the contents of your extra wrapper element..
Put the float code on the wrapper element and use
$(document).ready(function() {
$(".block-wrapper").click(function() {
$(this).siblings().find('.block').slideToggle("slow");
});
});
Demo at http://jsfiddle.net/gaby/t8GNP/
Update #1
If you need to move the clicked element to the top left and back, then you cannot really do it with CSS.
You will need to manually position them (through JS), set CSS transitions (or jquery), and apply the new positions once you click.
Later on you might want more than one to remain visible and reposition as well..
So you might want to take a look at the great Isotope plugin which can handle this and a multitude of more situations/layouts

Here is my version:
http://jsfiddle.net/selbh/dhcyA/92/
(only javascript is changed, and it's responsive)
$(document).ready(function() {
$(".block").click(function() {
var $this = $(this);
var pos = $this.offset();
var $siblings = $(this).siblings().add(this);
var marginTop = $this.css('marginTop').replace(/[^-\d\.]/g, '');
var marginLeft = $this.css('marginLeft').replace(/[^-\d\.]/g, '');
var $clone = $this.clone();
$siblings.slideToggle("slow");
$clone.css({
position: 'absolute',
left: pos.left - marginLeft,
top: pos.top - marginTop,
'background-color': $this.css('background-color')
});
$('body').append($clone);
$this.css('opacity', 0);
$clone.animate({
'left': 0,
'top': 0
});
$clone.click(function() {
$siblings.slideToggle("slow", function() {
$clone.remove();
$this.css('opacity', 1);
});
$clone.animate({
left: pos.left - marginLeft,
top: pos.top - marginTop
});
});
});
});​

I'm kind of sleepy(It's 2:30 AM here) so I leave the half done answer here to give you an idea (I did it in 30 minutes so I guess with 30 minutes more you can get something really nice)
http://jsfiddle.net/LuL2s/2/
The trick comes by the block-holder which make the ease animation and making a difference between when they appear and disappear
JS
$(document).ready(function() {
var open = true;
$(".block").click(function() {
var $this = $(this);
var count = 0;
if (open) {
$this.parent().siblings().children().slideToggle("slow", function(){
if (count++ == 2) {
$this.parent().siblings().animate({width: 'toggle', height:'toggle'});
}
});
} else {
$this.parent().siblings().animate({width: 'toggle', height:'toggle'}, function(){
if (count++ == 2) {
$this.parent().siblings().children().slideToggle("slow");
}
});
}
open = !open;
});
});
HTML
<div class="block-holder">
<div class="block">
<h2>I'm block 1</h2>
</div>
</div>
<div class="block-holder">
<div class="block">
<h2>I'm block 2</h2>
</div>
</div>
<div class="block-holder">
<div class="block">
<h2>I'm block 3</h2>
</div>
</div>
<div class="block-holder">
<div class="block">
<h2>I'm block 4</h2>
</div>
</div>
CSS
.block {
width: 100%;
height: 100%;
text-align: center;
line-height: 100px;
cursor: pointer;
}
.block-holder:nth-child(1) .block {
background: green;
}
.block-holder:nth-child(2) .block {
background: red;
}
.block-holder:nth-child(3) .block {
background: orange;
}
.block-holder:nth-child(4) .block {
background: pink;
}
.block-holder {
width: 200px;
height: 100px;
float: left;
margin: 20px;
}

Great Challenge!
New Version:
Here is a much better version as it makes the blocks stay in their rows. I added a css function so that your nth-child styles could be applied even in the rows. Even maintains same HTML Structure.
Demo: http://jsfiddle.net/MadLittleMods/fDDZB/23/
The jQuery for this new revision looks like:
$('.block').on('click', function() {
var block = $(this);
// Keep the blocks in line
makeRows($('body'));
$('.block').not(this).each(function() {
// If sibling on the same level, horizontal toggle
// We also want ignore the toggleMethod if it is shown because we might need to reassign
if (($(this).position().top == block.position().top && (($(this).data('toggle') == -1) || $(this).data('toggle') == null)) || ($(this).data('toggle') != -1 && $(this).data('toggleMethod') == 'side'))
{
$(this).data('toggleMethod', 'side');
// Hide block
if ($(this).data('toggle') == -1 || $(this).data('toggle') == null)
{
// Set properties for later use in show block
$(this).data('overflowBefore', $(this).css('overflow'));
$(this).css('overflow', 'hidden');
$(this).data('marginBefore', $(this).css('margin'));
var width = $(this).width();
$(this).animate({
width: 0,
margin: 0
}, function() {
$(this).data('toggle', width);
});
}
// Show block
else
{
$(this).css('overflow', $(this).data('overflowBefore'));
$(this).animate({
width: $(this).data('toggle'),
margin: $(this).data('marginBefore')
}, function() {
$(this).data('toggle', -1);
});
}
}
// Do a normal vertical toggle
else
{
$(this).data('toggleMethod', 'top');
$(this).slideToggle('slow');
}
});
});
// Make rows to make the blocks in line
function makeRows(container)
{
// Make rows so that the elements stay where they should
var containerWidth = container.width();
var currentRowWidth = 0;
// Add styles first so nothing gets messed up
container.children().each(function() {
var itemCSS = css($(this));
$(this).css(itemCSS);
});
// Now assemble the rows
container.children().each(function() {
var blockWidth = $(this).outerWidth() + parseInt($(this).css('margin-left')) + parseInt($(this).css('margin-right'));
if((currentRowWidth + blockWidth) < containerWidth)
{
currentRowWidth += blockWidth;
}
else
{
Array.prototype.reverse.call($(this).prevUntil('.row')).wrapAll('<div class="row"></div>');
$(this).prev().append('<div class="row_clear" style="clear: both;"></div>');
currentRowWidth = 0;
}
});
}
// Remove the rows added
function deleteRows()
{
var content = $('.row').contents()
$('.row').replaceWith(content);
$('.row_clear').remove();
}
$(window).resize(function() {
deleteRows();
});
// Functions courtesy of marknadal
// https://stackoverflow.com/a/5830517/796832
function css(a)
{
var sheets = document.styleSheets, o = {};
for(var i in sheets) {
var rules = sheets[i].rules || sheets[i].cssRules;
for(var r in rules) {
if(a.is(rules[r].selectorText)) {
o = $.extend(o, css2json(rules[r].style), css2json(a.attr('style')));
}
}
}
return o;
}
function css2json(css)
{
var s = {};
if(!css) return s;
if(css instanceof CSSStyleDeclaration) {
for(var i in css) {
if((css[i]).toLowerCase) {
s[(css[i]).toLowerCase()] = (css[css[i]]);
}
}
} else if(typeof css == "string") {
css = css.split("; ");
for (var i in css) {
var l = css[i].split(": ");
s[l[0].toLowerCase()] = (l[1]);
};
}
return s;
}
I added a makeRows and deleteRows functions so that the blocks would stay in their rows instead of getting smaller and moving into the row above. I call deleteRows whenever the window resizes so that it can maintain a responsive layout. Then if the blocks need to be toggled, I recreate the rows.
css and css2json functions are courtesy of marknadal
Old version:
I came up with a solution with .animate so that it could ease horizontally.
Here is a demo: http://jsfiddle.net/MadLittleMods/fDDZB/8/
The jQuery looks like:
$('.block').on('click', function() {
var block = $(this);
$(this).siblings().each(function() {
// If sibling on the same level, horizontal toggle
// We also want ignore the toggleMethod if it is shown because we might need to reassign
if (($(this).position().top == block.position().top && ($(this).data('toggle') == -1) || $(this).data('toggle') == null) || ($(this).data('toggle') != -1 && $(this).data('toggleMethod') == 'side'))
{
$(this).data('toggleMethod', 'side');
// Hide block
if ($(this).data('toggle') == -1 || $(this).data('toggle') == null)
{
// Set properties for later use in show block
$(this).data('overflowBefore', $(this).css('overflow'));
$(this).css('overflow', 'hidden');
$(this).data('marginBefore', $(this).css('margin'));
var width = $(this).width();
$(this).animate({
width: 0,
margin: 0
}, function() {
$(this).data('toggle', width);
});
}
// Show block
else
{
$(this).css('overflow', $(this).data('overflowBefore'));
$(this).animate({
width: $(this).data('toggle'),
margin: $(this).data('marginBefore')
}, function() {
$(this).data('toggle', -1);
});
}
}
// Do a normal vertical toggle
else
{
$(this).data('toggleMethod', 'top');
$(this).slideToggle('slow');
}
});
});​
The key was to separate the blocks that were toggled with .slideToggle and .animate because you have to apply the same when they show and hide.

Add/remove class with jquery based on vertical scroll?

So basically I'd like to remove the class from 'header' after the user scrolls down a little and add another class to change it's look.
Trying to figure out the simplest way of doing this but I can't make it work.
$(window).scroll(function() {
var scroll = $(window).scrollTop();
if (scroll <= 500) {
$(".clearheader").removeClass("clearHeader").addClass("darkHeader");
}
}
CSS
.clearHeader{
height: 200px;
background-color: rgba(107,107,107,0.66);
position: fixed;
top:200;
width: 100%;
}
.darkHeader { height: 100px; }
.wrapper {
height:2000px;
}
HTML
<header class="clearHeader"> </header>
<div class="wrapper"> </div>
I'm sure I'm doing something very elementary wrong.

$(window).scroll(function() {
var scroll = $(window).scrollTop();
//>=, not <=
if (scroll >= 500) {
//clearHeader, not clearheader - caps H
$(".clearHeader").addClass("darkHeader");
}
}); //missing );
Fiddle
Also, by removing the clearHeader class, you're removing the position:fixed; from the element as well as the ability of re-selecting it through the $(".clearHeader") selector. I'd suggest not removing that class and adding a new CSS class on top of it for styling purposes.
And if you want to "reset" the class addition when the users scrolls back up:
$(window).scroll(function() {
var scroll = $(window).scrollTop();
if (scroll >= 500) {
$(".clearHeader").addClass("darkHeader");
} else {
$(".clearHeader").removeClass("darkHeader");
}
});
Fiddle
edit: Here's version caching the header selector - better performance as it won't query the DOM every time you scroll and you can safely remove/add any class to the header element without losing the reference:
$(function() {
//caches a jQuery object containing the header element
var header = $(".clearHeader");
$(window).scroll(function() {
var scroll = $(window).scrollTop();
if (scroll >= 500) {
header.removeClass('clearHeader').addClass("darkHeader");
} else {
header.removeClass("darkHeader").addClass('clearHeader');
}
});
});
Fiddle

Pure javascript
Here's javascript-only example of handling classes during scrolling.
const navbar = document.getElementById('navbar')
// OnScroll event handler
const onScroll = () => {
// Get scroll value
const scroll = document.documentElement.scrollTop
// If scroll value is more than 0 - add class
if (scroll > 0) {
navbar.classList.add("scrolled");
} else {
navbar.classList.remove("scrolled")
}
}
// Use the function
window.addEventListener('scroll', onScroll)
#navbar {
position: fixed;
top: 0;
left: 0;
right: 0;
width: 100%;
height: 60px;
background-color: #89d0f7;
box-shadow: 0px 5px 0px rgba(0, 0, 0, 0);
transition: box-shadow 500ms;
}
#navbar.scrolled {
box-shadow: 0px 5px 10px rgba(0, 0, 0, 0.25);
}
#content {
height: 3000px;
margin-top: 60px;
}
<!-- Optional - lodash library, used for throttlin onScroll handler-->
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.js"></script>
<header id="navbar"></header>
<div id="content"></div>
Some improvements
You'd probably want to throttle handling scroll events, more so as handler logic gets more complex, in that case throttle from lodash lib comes in handy.
And if you're doing spa, keep in mind that you need to clear event listeners with removeEventListener once they're not needed (eg during onDestroy lifecycle hook of your component, like destroyed() for Vue, or maybe return function of useEffect hook for React).
Example throttling with lodash:
// Throttling onScroll handler at 100ms with lodash
const throttledOnScroll = _.throttle(onScroll, 100, {})
// Use
window.addEventListener('scroll', throttledOnScroll)

Add some transition effect to it if you like:
http://jsbin.com/boreme/17/edit?html,css,js
.clearHeader {
height:50px;
background:lightblue;
position:fixed;
top:0;
left:0;
width:100%;
-webkit-transition: background 2s; /* For Safari 3.1 to 6.0 */
transition: background 2s;
}
.clearHeader.darkHeader {
background:#000;
}

Its my code
jQuery(document).ready(function(e) {
var WindowHeight = jQuery(window).height();
var load_element = 0;
//position of element
var scroll_position = jQuery('.product-bottom').offset().top;
var screen_height = jQuery(window).height();
var activation_offset = 0;
var max_scroll_height = jQuery('body').height() + screen_height;
var scroll_activation_point = scroll_position - (screen_height * activation_offset);
jQuery(window).on('scroll', function(e) {
var y_scroll_pos = window.pageYOffset;
var element_in_view = y_scroll_pos > scroll_activation_point;
var has_reached_bottom_of_page = max_scroll_height <= y_scroll_pos && !element_in_view;
if (element_in_view || has_reached_bottom_of_page) {
jQuery('.product-bottom').addClass("change");
} else {
jQuery('.product-bottom').removeClass("change");
}
});
});
Its working Fine

Is this value intended? if (scroll <= 500) { ... This means it's happening from 0 to 500, and not 500 and greater. In the original post you said "after the user scrolls down a little"

In a similar case, I wanted to avoid always calling addClass or removeClass due to performance issues. I've split the scroll handler function into two individual functions, used according to the current state. I also added a debounce functionality according to this article: https://developers.google.com/web/fundamentals/performance/rendering/debounce-your-input-handlers
var $header = jQuery( ".clearHeader" );
var appScroll = appScrollForward;
var appScrollPosition = 0;
var scheduledAnimationFrame = false;
function appScrollReverse() {
scheduledAnimationFrame = false;
if ( appScrollPosition > 500 )
return;
$header.removeClass( "darkHeader" );
appScroll = appScrollForward;
}
function appScrollForward() {
scheduledAnimationFrame = false;
if ( appScrollPosition < 500 )
return;
$header.addClass( "darkHeader" );
appScroll = appScrollReverse;
}
function appScrollHandler() {
appScrollPosition = window.pageYOffset;
if ( scheduledAnimationFrame )
return;
scheduledAnimationFrame = true;
requestAnimationFrame( appScroll );
}
jQuery( window ).scroll( appScrollHandler );
Maybe someone finds this helpful.

For Android mobile $(window).scroll(function() and $(document).scroll(function() may or may not work. So instead use the following.
jQuery(document.body).scroll(function() {
var scroll = jQuery(document.body).scrollTop();
if (scroll >= 300) {
//alert();
header.addClass("sticky");
} else {
header.removeClass('sticky');
}
});
This code worked for me. Hope it will help you.

This is based of of #shahzad-yousuf's answer, but I only needed to compress a menu when the user scrolled down. I used the reference point of the top container rolling "off screen" to initiate the "squish"
<script type="text/javascript">
$(document).ready(function (e) {
//position of element
var scroll_position = $('div.mainContainer').offset().top;
var scroll_activation_point = scroll_position;
$(window).on('scroll', function (e) {
var y_scroll_pos = window.pageYOffset;
var element_in_view = scroll_activation_point < y_scroll_pos;
if (element_in_view) {
$('body').addClass("toolbar-compressed ");
$('div.toolbar').addClass("toolbar-compressed ");
} else {
$('body').removeClass("toolbar-compressed ");
$('div.toolbar').removeClass("toolbar-compressed ");
}
});
}); </script>