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What dose mean by "window.scrollY > 0"

window.addEventListener("scroll",()=>{
const header = document.querySelector("header");
header.classList.toggle("sticky", window.scrollY > 0);
})
I know about .toggle() method but not so clearly. Would some one please explain about toggle() and window.scrollY?

Scroll Down. scrollY property of the Window interface returns the number of pixels that the document is currently scrolled vertically.
window.addEventListener("scroll", (event) => {
document.querySelector("h1").textContent = this.scrollY;
document.querySelector("h2").textContent = ("sticky", window.scrollY > 0);
})
body {
width: 100vw;
height: 400vh;
}
h1 {
position: fixed;
top: 0;
}
h2 {
position: fixed;
top: 20%;
}
<h1>0</h1>
<h2></h2>

Move element by certain amount while scrolling

I want to move the white box to the right by 50% while scrolling until it reaches the red section. The distance to the red section is 1000px in the example.
The code below moves the box to the right as I scroll down, and I'm just using a random number 10 to slow down the movement but I can't get my head around to make it move evenly for every scroll event until the box reaches the red section and move 50% to the right.
var xPos = 0;
function getXPos(target, windowPos) {
var amount = windowPos - target;
xPos = amount / 10;
return xPos;
}
$(window).scroll(function() {
var windowPos = $(window).scrollTop();
var sectionOne = $('section.one').offset().top;
var sectionTwo = $('section.two').offset().top;
var box = $('.box');
if (windowPos > sectionOne && windowPos < sectionTwo) {
box.css({
"transform": 'translateX(' + getXPos(sectionOne, windowPos) + '%)'
});
}
});
body {
margin: 0;
}
.box {
background: white;
position: sticky;
top: 0;
width: 300px;
height: 300px;
}
section.one {
height: 1000px;
background: blue;
}
section.two {
height: 1000px;
background: red;
}
<section class="one">
<div class="box"></div>
</section>
<section class="two"></section>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
There is also another issue with scroll that if I scroll too fast, the box won't move as much.
Here is the fiddle for demonstration.
https://jsfiddle.net/sungsoonz/0Lspo2d9/

So I used the logic of making a progress bar for whole page but for your section with class "one". So when you scroll the section 100% of it's height the "left" css property on the div with class "box" becomes at value of "100%". But as I understood we need to stop moving when we reach section with class "two" with div with class "box". So {left: 100%} will become when we have scrolled whole section with class "box" minus the visible height of div with class "box". Then it is easily calculated to move only for 50% of width of section with class "one" (-width of div with class "box" width / 2 to center it). Hope I described my solution clearly (xd). Hope it helps
The code:
one = document.querySelector(".one")
two = document.querySelector(".two")
box = document.querySelector(".box")
$(window).on('scroll', function (){
if (window.scrollY >= (one.scrollHeight - box.offsetHeight)) {
$('.box').css('left', `calc(50% - ${(box.offsetWidth / 2)}px`);
return
}
$scrolledFrom = $(document).scrollTop();
$documentHeight = $(document).height() - ($(".two").height() + box.offsetHeight);
$leftOffset = ($scrolledFrom / $documentHeight) * 100;
$('.box').css('left', `calc(${($leftOffset / 2)}% - ${(box.offsetWidth / 2)}px`);
console.log ()
});
body {
margin: 0;
}
.box {
background: white;
position: sticky;
top: 0;
left: 0;
width: 300px;
height: 300px;
}
section.one {
height: 1000px;
background: blue;
}
section.two {
height: 1000px;
background: red;
}
<section class="one">
<div class="box"></div>
</section>
<section class="two"></section>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>

Cant get offset of div

this is my getoffset js code to get div width and left
var objRedPacketDivStyle = document.getElementById("styRedPacketAppear");
var objOffset = objRedPacketDivStyle.offset();
var intWidth = objOffset.offsetWidth;
var objWidthStart = objOffset.offset.left;
var objWidthEnd = objWidthStart + intWidth;
alert(objWidthStart + objWidthEnd);
and here is my div and css
<div class="styRedPacketAppear" id="styRedPacketAppear"></div>
#styRedPacketAppear {
position: fixed;
top: 0;
left: 0;
width: 100%;
z-index: 98;
pointer-events: none;
}

This isn't working as .offset() is a jQuery method. Since you don't have jquery you need to use vanilla javascript to achieve this.
You can use:
element.offsetWidth: "returns the layout width of an element as an integer." - MDN
element.offsetLeft: "returns the number of pixels that the upper left corner of the current element is offset to the left within the HTMLElement.offsetParent node." - MDN
Using these two properties will resolve your issue:
var objRedPacketDivStyle = document.getElementById("styRedPacketAppear");
// Remove this: var objOffset = objRedPacketDivStyle.position.offset();
var intWidth = objRedPacketDivStyle.offsetWidth;
var objWidthStart = objRedPacketDivStyle.offsetLeft;
var objWidthEnd = objWidthStart + intWidth;
alert(objWidthStart + objWidthEnd);
#styRedPacketAppear {
position: fixed;
top: 0;
left: 0;
width: 100%;
z-index: 98;
pointer-events: none;
}
<div class="styRedPacketAppear" id="styRedPacketAppear"></div>

The offsetTop property returns the top position (in pixels) relative to the top of the offsetParent element.
The returned value includes:
-the top position, and margin of the element
-the top padding, scrollbar and border of the offsetParent element.
#test {
top: 100px;
margin: 10px;
padding: 10px;
width: 300px;
position: fixed;
border: 5px solid black
}
var testDiv = document.getElementById("test");
document.getElementById("demo").innerHTML = testDiv.offsetTop;
Result-offsetTop is: 110

Fix Section when reaches top. Unfix when previous section is visible

I'm trying to stick a section to the top when it hits the top of the browser on scroll down, but I'd like to unstick it when the user scrolls back up and the previous section is back in view.
I'm detecting distance from top to section I'd like to stick, but once its at the top how do we detect user scrolling back up and previous section comes back into view.
My Codepen: https://codepen.io/omarel/pen/LeEjax
Snippet
$(window).on('scroll', function() {
var scrollTop = $(window).scrollTop();
sectionone = $('section.one').offset().top;
sectiontwo = $('section.two').offset().top;
sectiontwodistance = (sectiontwo - scrollTop);
sectiononedistance = (sectionone - scrollTop);
console.log(sectiononedistance);
if (sectiontwodistance < 1) {
$('section.two').addClass('fix');
}
});
html,
body {
width: 100%;
height: 100%;
}
section {
height: 100%;
border: 5px solid red;
position: absolute;
width: 100%;
}
section.one {
z-index: 1;
top: 0%;
}
section.two {
border: 5px solid green;
z-index: 2;
top: 100%;
}
section.three {
z-index: 3;
top: 200%;
}
section.fix {
position: fixed;
top: 0;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<section class="one">
1
</section>
<section class="two">
2
</section>
<section class="three">
3
</section>

I would update your jQuery to the snippet below. It checks the position of section one against the height of the window and if less than, or equal to it removes the .fix class.
$(window).on('scroll', function() {
var scrollTop = $(window).scrollTop();
sectionone = $('section.one').offset().top;
sectiontwo = $('section.two').offset().top;
sectiontwodistance = (sectiontwo - scrollTop);
sectiononedistance = (sectionone - scrollTop);
console.log(sectiononedistance);
if (sectiontwodistance < 1) {
$('section.two').addClass('fix');
}
if (Math.abs(sectiononedistance) <= $(window).height()) {
$('section.two').removeClass('fix');
}
});

Stick div at top not working properly : javascript

I going to create a scroll and stick div which has to stick on the top of the page but while scrolling down the div next to stickdiv automatically stick to the div before to sticky div
var left = document.getElementsByClassName("stickdiv");
for (var i = 0; i < left.length; i++) {
var stop = (left[0].offsetTop);
window.onscroll = function(e) {
var scrollTop = (window.pageYOffset !== undefined) ? window.pageYOffset : (document.documentElement || document.body.parentNode || document.body).scrollTop;
// left.offsetTop;
if (scrollTop >= stop) {
// get array item by index
left[0].classList.add('stick'); //adding a class name
} else {
// get array item by index
left[0].classList.remove('stick');
}
}
}
.stickdiv {
height: 50vh!important;
width: 100vh!important;
background-color: green!important;
}
.stick {
position: fixed;
top: 0;
margin: 0 0
}
#right {
float: right;
width: 100px;
height: 1000px;
background: red;
}
.des {
height: 300px;
width: 100%;
background-color: #000;
}
<div class="des"></div>
<div class="stickdiv"></div>
<div id="right"></div>
Example : green color div is the sticky div but after scrollingdown , red is also going to stick , I've tried position absolute in css but not working how to fix it

Here is the code to make green sticky when scrolling.
$ = document.querySelectorAll.bind(document);
// how far is the green div from the top of the page?
var initStickyTop = $(".stickdiv")[0].getBoundingClientRect().top + pageYOffset;
// clone the green div
var clone = $(".stickdiv")[0].cloneNode(true);
// hide it first
clone.style.display = "none";
// add it to dom
document.body.appendChild(clone);
addEventListener("scroll",stick=function() {
// if user scroll past the sticky div
if (initStickyTop < pageYOffset) {
// hide the green div but the div still take up the same space as before so scroll position is not changed
$(".stickdiv")[0].style.opacity = "0";
// make the clone sticky
clone.classList.add('stick');
// show the clone
clone.style.opacity="1";
clone.style.display = "block";
} else {
// make the clone not sticky anymore
clone.classList.remove("stick");
// hide it
clone.style.display = "none";
// show the green div
$(".stickdiv")[0].style.opacity="1";
};
});
// when resize, recalculate the position of the green div
addEventListener("resize", function() {
initStickyTop = $(".stickdiv")[0].getBoundingClientRect().top + pageYOffset;
stick();
});
.stickdiv {
height: 50vh!important;
width: 100vh!important;
background-color: green!important;
}
.stick {
position: fixed;
top: 0;
margin: 0 0
}
#right {
float: right;
width: 100px;
height: 1000px;
background: red;
}
.des {
height: 300px;
width: 100%;
background-color: #000;
}
<div class="des"></div>
<div class="stickdiv"></div>
<div id="right"></div>

JS FIDDLE
you might want to remove the stickdiv class and add it accordingly
if (scrollTop >= stop) {
// get array item by index
left[0].classList.add('stick'); //adding a class name
left[0].classList.remove('stickdiv');
} else {
// get array item by index
left[0].classList.remove('stick');
left[0].classList.add('stickdiv');
}