The problem with this parallax is that it runs on all sections of the .parallaxBg class page at the same time.
Therefore, I would like to use the Intersection Observer to run parallax only when the section enters the viewport.
// Parallax -------------------------------------------------------------------------
window.addEventListener("scroll", function parallaxFunction() {
let bg = document.querySelectorAll(".parallaxBg");
let distance = window.pageYOffset;
bg.forEach(parallaxBg => {
parallaxBg.style.top = distance * -0.2 + "px";
})
});
// Intersection observer --------------------------------------------------------------
const bgImages = document.querySelectorAll('.parallaxBg');
observer = new IntersectionObserver((entries) => {
entries.forEach(entry => {
console.log(entries);
if (entry.intersectionRatio > 0) {
entry.target.parallaxFunction;
} else {
entry.target.parallaxFunction;
}
});
});
bgImages.forEach(image => {
observer.observe(image);
});
Yo. Bit late to the party but I needed to figure this out today. Three essential parts to this:
Intersection Observer tracks when the parallax class is in the viewport.
Scroll listener gets triggered when the parallax class is in the viewport, and is removed when the parallax class leaves the viewport.
While the scroll listener is active, we update the transform based on the scroll position
I'm running this through a debounce function to make it slightly smoother, but this is optional.
I think the top position can be calculated better, and I'd be interested to know how we can optimise this, but this answers your question of how to only transform the element when it is in the viewport - you can look in the console and check the dynamically added css inline on the img tag - ONLY when in the viewport :)
document.addEventListener('DOMContentLoaded', function () {
var parallaxImages =[].slice.call(
document.querySelectorAll(".parallax img")
)
console.log(parallaxImages);
if ("IntersectionObserver" in window && 'IntersectionObserverEntry' in window) {
// Intersection Observer Configuration
const observerOptions = {
root: null,
rootMargin: '0px 0px', // important: needs units on all values
threshold: 0
};
var observer = new IntersectionObserver(handleIntersect, observerOptions);
var el;
function handleIntersect(entries, observer) {
entries.forEach(function(entry) {
if (entry.isIntersecting) {
el = entry.target;
window.addEventListener('scroll', parallax, false);
} else {
window.removeEventListener('scroll', parallax, false);
}
});
}
parallaxImages.forEach(function(parallaxImage) {
observer.observe(parallaxImage);
});
var parallax = debounce(function() {
amount = Math.round( window.pageYOffset * 0.2 );
el.style.webkitTransform = 'translateY(-'+amount+'px)';
}, 10);
}
}, false);
/*************************************
Function: Debounce
*************************************/
function debounce(func, wait, immediate) {
var timeout;
return function() {
var context = this, args = arguments;
var later = function() {
timeout = null;
if (!immediate) func.apply(context, args);
};
var callNow = immediate && !timeout;
clearTimeout(timeout);
timeout = setTimeout(later, wait);
if (callNow) func.apply(context, args);
};
};
/* PARALLAX STYLING */
.parallax {
height: 40vh;
overflow: hidden;
}
.parallax img {
width: 100%;
}
/* NICE TO HAVE */
body {
margin: 0;
padding: 0;
font-family: arial;
}
h1 {
margin: 0;
color: white;
}
header {
height: 110vh;
background-color: steelblue;
display: flex;
justify-content: center;
align-items: center;
}
section.spacer {
height: 110vh;
background-color: seagreen;
display: flex;
justify-content: center;
align-items: center;
}
footer {
height: 50vh;
background-color: firebrick;
}
<header>
<h1>Scroll down!</h1>
</header>
<main>
<section class="parallax">
<img src="https://picsum.photos/1920/1920" alt="">
</section>
<section class="spacer">
<h1>Keep scrolling!</h1>
</section>
<section class="parallax">
<img src="https://picsum.photos/1920/1920" alt="">
</section>
</main>
<footer></footer>
Related
i'm trying to build my own simple fullpage.js or something similar, just so I can learn more about how to use requestAnimationFrame function, however I am stuck into this problem of transform3d value resetting, which behaves like this
You can see in the gif that every time I switch slides, the animation starts always at the first slide
Here is the implementation of the slider
html
<div class="scroller">
<div class="scroller-content">
<section class="scroller-section s1">SLIDE 1</section>
<section class="scroller-section s2">SLIDE 2</section>
<section class="scroller-section s3">SLIDE 3</section>
<section class="scroller-section s4">SLIDE 4</section>
</div>
</div>
css
.scroller {
width: 100vw;
height: 100vh;
overflow-y: hidden;
}
.scroller-section {
width: 100vw;
height: 100vh;
display: flex;
text-align: center;
align-items: center;
justify-content: center;
font-size: 25rem;
}
.scroller-section.s1 {
background-color: #535bf2;
}
.scroller-section.s2 {
background-color: #242424;
}
.scroller-section.s3 {
background-color: #213547;
}
.scroller-section.s4 {
background-color: #747bff;
}
const scrollerContent = document.querySelector(".scroller-content")
const offsets = [0, -100, -200, -300]
let index = 0
window.addEventListener("wheel", (e) => {
if (e.deltaY > 0) {
index = shift(index + 1) // go next
const offset = offsets[index]
createAnimationFrames((delta) => {
scrollerContent.style.transform = `translate3d(0, ${delta * offset}vh,0)`
}, 1000)
} else if (e.deltaY < 0) {
index = shift(index - 1) // go prev
const offset = offsets[index]
createAnimationFrames((delta) => {
scrollerContent.style.transform = `translate3d(0, ${delta * offset}vh,0)`
}, 1000)
}
})
Here is the implementation of createAnimationFrames
const createAnimationFrames = (callback: (delta: number) => void, duration: number) => {
let start = new Date();
let raf = requestAnimationFrame;
const animate = () => {
let now = new Date();
const delta = Math.min((now.getTime() - start.getTime()) / duration, 1);
callback(delta);
if (delta < 1) {
raf(animate);
}
};
raf(animate);
};
Basically it runs the callback every frame request and the callback takes delta as a reference for the progress of the animation.
The thing is that it works normally by just having a simple reassign to the transform attribute and not using the requestAnimationFrame. Any solutions for this?
I'm trying to come up with a cross-device code that handles pointer events.
I'm running this code successfully on Chrome/Android (using USB debugging), but the Chrome desktop just acts up and keeps firing pointermove after the mouse has been released.
(Another problem is that the moves are not as smooth as on the mobile)
Playable demo
These SO posts don't solve my problem:
event-listener-with-pointerup-not-firing-when-activated-from-touchscreen
pointerup-event-does-not-fire-for-mouse-actions-on-a-link-when-pointermove-has-b
The "pointerup" Event is assigned to the #canvas, but such event will never occur because the mouse is actually above the generated DIV circle.
Since your circles are just visual helpers, set in CSS
.dot {
/* ... */
pointer-events: none;
}
Also, make sure to use Event.preventDefault() on "pointerdown".
Regarding the other strategies for a seamless experience, both on desktop and on mobile (touch):
assign only the "pointerdown" Event to a desired Element (canvas in your case)
use the window object for all the other events
Edited example:
const canvas = document.getElementById('canvas');
function startTouch(ev) {
ev.preventDefault();
const dot = document.createElement('div');
dot.classList.add('dot');
dot.id = ev.pointerId;
dot.style.left = `${ev.pageX}px`;
dot.style.top = `${ev.pageY}px`;
document.body.append(dot);
}
function moveTouch(ev) {
const dot = document.getElementById(ev.pointerId);
if (!dot) return;
dot.style.left = `${ev.pageX}px`;
dot.style.top = `${ev.pageY}px`;
}
function endTouch(ev) {
const dot = document.getElementById(ev.pointerId);
if (!dot) return;
removeDot(dot);
}
function removeDot(dot) {
dot.remove();
}
canvas.addEventListener('pointerdown', startTouch);
addEventListener('pointermove', moveTouch);
addEventListener('pointerup', endTouch);
addEventListener('pointercancel', endTouch);
.dot {
background-color: deeppink;
width: 2rem;
height: 2rem;
border-radius: 50%;
transform: translate(-50%, -50%);
position: absolute;
pointer-events: none; /* ADD THIS! */
}
#canvas {
height: 50vh;
background-color: black;
touch-action: none;
}
body {
margin: 0;
}
<div id="canvas"></div>
The code needs also this improvement:
Don't query the DOM inside a pointermove event
Using CSS vars
As per the comments section here's a viable solution that uses custom properties CSS variables and JS's CSSStyleDeclaration.setProperty() method.
Basically the --x and --y CSS properties values are updated from the pointerdown/move event handlers to reflect the current clientX and clientY values:
const el = (sel, par) => (par || document).querySelector(sel);
const elNew = (tag, prop) => Object.assign(document.createElement(tag), prop);
const canvas = document.getElementById('canvas');
const pointersDots = (parent) => {
const elParent = typeof parent === "string" ? el(parent) : parent;
const dots = new Map();
const moveDot = (elDot, {clientX: x,clientY: y}) => {
elDot.style.setProperty("--x", x);
elDot.style.setProperty("--y", y);
};
const onDown = (ev) => {
ev.preventDefault();
const elDot = elNew("div", { className: "dot" });
moveDot(elDot, ev);
elParent.append(elDot);
dots.set(ev.pointerId, elDot);
};
const onMove = (ev) => {
if (dots.size === 0) return;
const elDot = dots.get(ev.pointerId);
moveDot(elDot, ev);
};
const onUp = (ev) => {
if (dots.size === 0) return;
const elDot = dots.get(ev.pointerId);
elDot.remove();
dots.delete(ev.pointerId);
};
canvas.addEventListener('pointerdown', onDown);
addEventListener('pointermove', onMove);
addEventListener('pointerup', onUp);
addEventListener('pointercancel', onUp);
};
// Init: Pointers helpers
pointersDots("#canvas");
* {
margin: 0;
}
.dot {
--x: 0;
--y: 0;
pointer-events: none;
position: absolute;
width: 2rem;
height: 2rem;
border-radius: 50%;
background-color: deeppink;
transform: translate(-50%, -50%);
left: calc(var(--x) * 1px);
top: calc(var(--y) * 1px);
}
#canvas {
margin: 10vh;
height: 80vh;
background-color: black;
touch-action: none;
}
<div id="canvas"></div>
I am working on my portfolio website and I am a complete beginner in Javascript.
I would like a button which has its position fixed, to slowly fade in when I scroll down (suppose when I scroll to >=20px from the top of the document, it should fade in) and when I scroll back up to the original position, it should gradually fade out.
I have already tried my hand and written a code for this. It is working perfectly when you scroll down and up. But when you quickly scroll and stop scrolling in the mid-way, it behaves pretty abnormally (suddenly appears or disappears).
HTML:
<div class="a_large_page">
<div class="enclose bordar black" id="bottomtoup">hello</div>
</div>
JS:
mybutton = document.getElementById("bottomtoup")
// initially, the button stays hidden
visible = false
// When the user scrolls down 20px from the top of the document, show the button
window.onscroll = function() {
scrollFunction()
};
function scrollFunction() {
if (document.body.scrollTop > 20 || document.documentElement.scrollTop > 20) {
if (!visible) { // if the button is not visible,
unfade(mybutton); // function to gradually fadein button
visible = true; // button is visible so, set visible = false to true.
}
} else {
if (visible) { // if the button is visible,
fade(mybutton); // function to gradually fadeout button
visible = false; // set visible = true back to false
}
}
}
function unfade(element) {
var op = 0.1; // initial opacity
element.style.display = 'flex';
var timer = setInterval(function() {
if (op >= 1) {
clearInterval(timer);
}
element.style.opacity = op;
element.style.filter = 'alpha(opacity=' + op * 100 + ")";
op += op * 0.1;
}, 10);
}
function fade(element) {
var op = 1; // initial opacity
var timer = setInterval(function() {
if (op <= 0.1) {
clearInterval(timer);
element.style.display = 'none';
}
element.style.opacity = op;
element.style.filter = 'alpha(opacity=' + op * 100 + ")";
op -= op * 0.1;
}, 50);
}
Here is the fiddle: https://jsfiddle.net/P0intMaN/Lmp6u5ft/23/
My code is pretty substandard for sure. That's why it is behaving in this way. Hence, I am looking for an efficient way to achieve this. I have seen people making use of JQuery to do this, but I don't know JQuery at all. So, it would be much appreciated if the code is in pure JS.
I've changed your code and removed setInterval usage. This can be solved with it but may be harder to understand for newer coders.
There are also flags to keep track of whether you are currently fading or unfading to ensure you do not stack or "overlap" timeout/intervals.
mybutton = document.getElementById("bottomtoup")
// initially, the button stays hidden
var visible = false
// When the user scrolls down 20px from the top of the document, show the button
window.onscroll = function() {
scrollFunction()
};
function scrollFunction() {
var threshold = 20;
var below_threshold = document.body.scrollTop > threshold || document.documentElement.scrollTop > threshold;
if (below_threshold) {
if (!visible) { // if the button is not visible,
unfade(mybutton); // function to gradually fadein button
}
return;
}
if (visible) { // if the button is visible,
fade(mybutton); // function to gradually fadeout button
}
}
var current_opacity = 0.1;
var is_unfading = false;
var is_fading = false;
function unfade(element) {
if(!visible){
element.style.display = 'flex';
visible = true;
}
is_fading = false;
is_unfading = true;
unfade_step(element);
}
function unfade_step(element){
element.style.opacity = current_opacity;
element.style.filter = 'alpha(opacity=' + current_opacity * 100 + ")";
if (current_opacity >= 1){
// end
is_unfading = false;
current_opacity = 1;
return;
}
current_opacity += 0.01;
if(is_unfading){
setTimeout(function(){
unfade_step(element);
}, 10);
}
}
function fade(element) {
if(!visible){
return;
}
is_fading = true;
is_unfading = false;
fade_step(element);
}
function fade_step(element) {
element.style.opacity = current_opacity;
element.style.filter = 'alpha(opacity=' + current_opacity * 100 + ")";
if (current_opacity <= 0.001){
// end
is_fading = false;
visible = false;
current_opacity = 0.1;
element.style.display = 'none';
return;
}
current_opacity -= 0.01;
if(is_fading){
setTimeout(function(){
fade_step(element);
}, 10);
}
}
There is no need to have so much JS when you can do in so little:
If you feel to change the timing of
// Set a function onscroll - this will activate if the user scrolls
window.onscroll = function() {
// Set the height to check for
var appear = 20
if (window.pageYOffset >= appear) {
// If more show the element
document.getElementById("bottomtop").style.opacity = '1'
document.getElementById("bottomtop").style.pointerEvents = 'all'
} else {
// Else hide it
document.getElementById("bottomtop").style.opacity = '0'
document.getElementById("bottomtop").style.pointerEvents = 'none'
}
}
.a_large_page{
background-color: gray;
height: 2000px;
}
.enclose{
height: 40px;
width: 40px;
position:fixed;
margin-right: 20px;
margin-bottom: 20px;
right:0;
bottom:0;
pointer-events:none;
opacity:0;
justify-content: center;
align-items: center;
color:white;
/* This determines how fast animation takes place, you can change it as per your choice. */
transition:all 0.6s;
}
.enclose:hover{
cursor: pointer;
}
<div class="a_large_page">
<div class="enclose bordar black" id="bottomtop">hello</div>
</div>
There is no need to sense the scroll event in more modern browsers as you can use IntersetionObserver to tell you when scrolling has gone past 20px;
You can do this by placing a tiny element at the top of the page with height 20px. You then ask the system to tell you when this has gone out of, or comes back into, the viewport. At these points you can set the opacity of the Hello to 1 or 0 as appropriate.
The extra bonus is that you get rid of a lot of code and there isn't the possible clash between set intervals as we use transition on the opacity to do the gradual fade in/out.
// See MDN for more info on IntersectioObserver
let callback = (entries, observer) => {
entries.forEach(entry => {
if (entry.isIntersecting) {
mybutton.style.opacity = 0;
} else {
mybutton.style.opacity = 1;
}
});
};
const mybutton = document.getElementById("bottomtoup")
const observer = new IntersectionObserver(callback);
const observed = document.getElementById("observed");
observer.observe(observed);
.a_large_page {
background-color: gray;
height: 2000px;
position: relative;
}
#observed {
position: absolute;
top: 0;
left: 0;
height: 20px;
width: 10px;
z-index: -999;
}
.enclose {
height: 40px;
width: 40px;
position: fixed;
margin-right: 20px;
margin-bottom: 20px;
right: 0;
bottom: 0;
justify-content: center;
align-items: center;
color: white;
opacity: 0;
transition: opacity 1s linear;
}
<div class="a_large_page">
<div id="observed"></div>
<div class="enclose bordar black" id="bottomtoup">hello</div>
</div>
I'm trying to make an image slider. But as you can see the distance between the first and last element is not consistent. If you keep on dragging to left, the distance decreases and if you keep on dragging to right, the distance increases. Looks like the code is behaving differently on different zoom levels (sometimes?) and hence distance between every elements is changing at times.
//project refers to placeholder rectangular divs
projectContainer = document.querySelector(".project-container")
projects = document.querySelectorAll(".project")
elementAOffset = projects[0].offsetLeft;
elementBOffset = projects[1].offsetLeft;
elementAWidth = parseInt(getComputedStyle(projects[0]).width)
margin = (elementBOffset - (elementAOffset + elementAWidth))
LeftSideBoundary = -(elementAWidth)
RightSideBoundary = (elementAWidth * (projects.length)) + (margin * (projects.length))
RightSidePosition = RightSideBoundary - elementAWidth;
initialPosition = 0; //referring to mouse
mouseIsDown = false
projectContainer.addEventListener("mousedown", e => {
mouseIsDown = true
initialPosition = e.clientX;
})
projectContainer.addEventListener("mouseup", e => {
mouseExit(e)
})
projectContainer.addEventListener("mouseleave", e => {
mouseExit(e);
})
function mouseExit(e) {
mouseIsDown = false
//updates translateX value of transform
projects.forEach(project => {
var style = window.getComputedStyle(project)
project.currentTranslationX = (new WebKitCSSMatrix(style.webkitTransform)).m41
project.style.transform = 'translateX(' + (project.currentTranslationX) + 'px)'
})
}
projectContainer.addEventListener("mousemove", e => {
if (!mouseIsDown) { return };
// adds mousemovement to translateX
projects.forEach(project => {
project.style.transform = 'translateX(' + ((project.currentTranslationX ?? 0) + (e.clientX - initialPosition)) + 'px)'
shiftPosition(e, project)
})
})
//teleports div if it hits left or right boundary to make an infinite loop
function shiftPosition(e, project) {
projectStyle = window.getComputedStyle(project)
projectTranslateX = (new WebKitCSSMatrix(projectStyle.webkitTransform)).m41
//projectVisualPosition is relative to the left border of container div
projectVisualPosition = project.offsetLeft + projectTranslateX
if (projectVisualPosition <= LeftSideBoundary) {
project.style.transform = "translateX(" + ((RightSidePosition - project.offsetLeft)) + "px)"
updateTranslateX(e);
}
if (projectVisualPosition >= RightSidePosition) {
newPosition = -1 * (project.offsetLeft + elementAWidth)
project.style.transform = "translateX(" + newPosition + "px)"
updateTranslateX(e);
}
}
function updateTranslateX(e) {
projects.forEach(project => {
style = window.getComputedStyle(project)
project.currentTranslationX = (new WebKitCSSMatrix(style.webkitTransform)).m41
project.style.transform = 'translateX(' + (project.currentTranslationX) + 'px)'
initialPosition = e.clientX
})
}
*, *::before, *::after{
margin:0px;
padding:0px;
box-sizing: border-box;
font-size:0px;
user-select: none;
}
.project-container{
font-size: 0px;
position: relative;
width:1500px;
height:400px;
background-color: rgb(15, 207, 224);
margin:auto;
margin-top:60px;
white-space: nowrap;
overflow: hidden;
padding-left:40px;
padding-right:40px;
}
.project{
font-size:100px;
margin:40px;
display: inline-block;
height:300px;
width:350px;
background-color:red;
border: black 3px solid;
user-select: none;
}
<div class="project-container">
<div class="project">1</div>
<div class="project">2</div>
<div class="project">3</div>
<div class="project">4</div>
<div class="project">5</div>
<div class="project">6</div>
<div class="project">7</div>
<div class="project">8</div>
</div>
I'm not sure exactly how you would go about fixing your implementation. I played around with it for a while and discovered a few things; dragging more quickly makes the displacement worse, and the displacement seems to happen mainly when the elements are teleported at each end of the container.
I would guess that the main reason for this is that you are looping over all the elements and spacing them individually. Mouse move events generally happen under 20ms apart, and you are relying on all the DOM elements being repainted with their new transform positions before the next move is registered.
I did come up with a different approach using absolutely placed elements and the IntersectionObserver API, which is now supported in all modern browsers. The idea here is basically that when each element intersects with the edge of the container, it triggers an array lookup to see if the next element in the sequence is on the correct end and moves it there if not. Elements are only ever spaced by a static variable, while the job of sliding them is passed up to a new parent wrapper .project-slider.
window.addEventListener('DOMContentLoaded', () => {
// Style variables
const styles = {
width: 350,
margin: 40
};
const space = styles.margin*2 + styles.width;
// Document variables
const projectContainer = document.querySelector(".project-container");
const projectSlider = document.querySelector(".project-slider");
const projects = Array.from(document.querySelectorAll(".project"));
// Mouse interactions
let dragActive = false;
let prevPos = 0;
projectContainer.addEventListener('mousedown', e => {
dragActive = true;
prevPos = e.clientX;
});
projectContainer.addEventListener('mouseup', () => dragActive = false);
projectContainer.addEventListener('mouseleave', () => dragActive = false);
projectContainer.addEventListener('mousemove', e => {
if (!dragActive) return;
const newTrans = projectSlider.currentTransX + e.clientX - prevPos;
projectSlider.style.transform = `translateX(${newTrans}px)`;
projectSlider.currentTransX = newTrans;
prevPos = e.clientX;
});
// Generate initial layout
function init() {
let workingLeft = styles.margin;
projects.forEach((project, i) => {
if (i === projects.length - 1) {
project.style.left = `-${space - styles.margin}px`;
} else {
i !== 0 && (workingLeft += space);
project.style.left = `${workingLeft}px`;
};
});
projectSlider.currentTransX = 0;
};
// Intersection observer
function observe() {
const callback = (entries, observer) => {
entries.forEach(entry => {
if (entry.isIntersecting) {
// Find intersecting edge
const { left } = entry.boundingClientRect;
const isLeftEdge = left < projectContainer.clientWidth - left;
// Test and reposition next element
const targetIdx = projects.findIndex(project => project === entry.target);
let nextIdx = null;
const nextEl = () => projects[nextIdx];
const targetLeft = parseInt(entry.target.style.left);
const nextLeft = () => parseInt(nextEl().style.left);
if (isLeftEdge) {
nextIdx = targetIdx === 0 ? projects.length-1 : targetIdx - 1;
nextLeft() > targetLeft && (nextEl().style.left = `${targetLeft - space}px`);
} else {
nextIdx = targetIdx === projects.length-1 ? 0 : targetIdx + 1;
nextLeft() < targetLeft && (nextEl().style.left = `${targetLeft + space}px`);
};
};
});
};
const observer = new IntersectionObserver(callback, {root: projectContainer});
projects.forEach(project => observer.observe(project));
};
init();
observe();
});
*, *::before, *::after{
margin:0px;
padding:0px;
box-sizing: border-box;
font-size:0px;
user-select: none;
}
.project-container {
font-size: 0px;
width: 100%;
height: 400px;
background-color: rgb(15, 207, 224);
margin:auto;
margin-top:60px;
white-space: nowrap;
overflow: hidden;
}
.project-slider {
position: relative;
}
.project {
font-size:100px;
display: block;
position: absolute;
top: 40px;
height:300px;
width:350px;
background-color:red;
border: black 3px solid;
user-select: none;
}
<div class="project-container">
<div class="project-slider">
<div class="project">1</div>
<div class="project">2</div>
<div class="project">3</div>
<div class="project">4</div>
<div class="project">5</div>
<div class="project">6</div>
<div class="project">7</div>
<div class="project">8</div>
</div>
</div>
There is still an issue here which is how to resize the elements for smaller screens, and on browser resizes. You would have to add another event listener for window resizes which resets the positions and styles at certain breakpoints, and also determine the style variables programmatically when the page first loads. I believe this would still have been a partial issue with the original implementation so you'd have to address it at some point either way.
I want a counter animation which is triggered only when webpage reaches that certain part. For example, the js file would be this. I want the count to start only when the page reaches that certain section.
const counters = document.querySelectorAll('.counter');
const speed = 200; // The lower the slower
counters.forEach(counter => {
const updateCount = () => {
const target = +counter.getAttribute('data-target');
const count = +counter.innerText;
// Lower inc to slow and higher to slow
const inc = target / speed;
// console.log(inc);
// console.log(count);
// Check if target is reached
if (count < target) {
// Add inc to count and output in counter
counter.innerText = count + inc;
// Call function every ms
setTimeout(updateCount, 1);
} else {
counter.innerText = target;
}
};
updateCount();
});
Yo can easily do it using Jquery
$(document).ready(function() {
$(window).scroll(function() {
if ($(document).scrollTop() > 50) {
$("div").css("background-color", "#111111");
} else {
$("div").css("background-color", "transparent");
}
});
});
div {
height: 120vh;
transition-duration: 0.5s;
}
<div>
Scroll to Change Background
</div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.0/jquery.min.js"></script>
You can use Intersection Observer to do that
const $observeSection = document.querySelector('#second');
const options = {
root: null,
rootMargin: '0px',
threshold: 0.5
};
const observer = new IntersectionObserver(entries => {
entries.forEach(entry => {
if (entry.intersectionRatio > options.threshold) {
$observeSection.classList.add('yellow');
} else {
$observeSection.classList.remove('yellow');
}
});
}, options);
observer.observe($observeSection);
main {
display: flex;
flex-direction: column;
height: 100%;
width: 100%;
}
main section {
width: 100vw;
height: 100vh;
}
#first {
background: red;
}
#second {
background: blue;
}
#third {
background: green;
}
.yellow {
background: yellow!important;
}
<main>
<section id="first"></section>
<section id="second"></section>
<section id="third"></section>
</main>
In this example, I observe the second section, and when the scroll come to the middle of the section (threshold: 0.5), I add a class to change the color of this section.
Be careful if you need to handle legacies browsers as you can see here :
https://caniuse.com/#feat=intersectionobserver
You don't need jquery to achieve this.
Here is a VanillaJS solution:
window.onscroll = (e) => {
e.stopPropagation();
window.pageYOffset > 50 && console.log("do smh");
}