So I'm working on showing/hiding a nav element based on scrolling behavior. Once the user scrolls and scrolls past the nav element, I add a class to make it sticky but keep it out of view. Then once the user stops scrolling I add another class to the transition the element into view. Once the user scrolls again that class needs to be removed again and the nav disappears again.
This is the JS
let mobile_toolbar = document.querySelector(".mobile-toolbar");
let mobile_toolbar_top = (mobile_toolbar.offsetTop) + 50;
let scrollpos = window.scrollY;
let timer = null;
window.addEventListener(
"scroll",
function () {
scrollpos = window.scrollY;
console.log(timer)
if (timer !== null) {
if (scrollpos > mobile_toolbar_top) {
mobile_toolbar.classList.add("mobile-toolbar__hidden");
mobile_toolbar.classList.remove("mobile-toolbar--fixed");
clearTimeout(timer);
} else {
mobile_toolbar.classList.remove("mobile-toolbar__hidden");
mobile_toolbar.classList.remove("mobile-toolbar--fixed");
clearTimeout(timer);
}
}
if (scrollpos > mobile_toolbar_top) {
timer = setTimeout(function () {
mobile_toolbar.classList.add("mobile-toolbar--fixed");
}, 400);
}
},
false
);
As you can see I'm setting a timer to detect when the user stops scrolling and also check the scroll position to determine whether the add the fixed class or not. However, this isn't quite working as I'd like as the nav once slides down as soon as I scroll past itself and then disappears again as the timer is already not null at this point. Can anyone tell me what's wrong with my cod or if there's a better way to detect when the user has stopped scrolling? Vanilla JS only please as I'm trying not to use jQuery
you can refer a below code (it's tell you when user stop scrolling)
<html>
<body onscroll="bodyScroll();">
<script language="javascript">
var scrollTimer = -1;
function bodyScroll() {
document.body.style.backgroundColor = "white";
if (scrollTimer != -1)
clearTimeout(scrollTimer);
scrollTimer = window.setTimeout("scrollFinished()", 500);
}
function scrollFinished() {
document.body.style.backgroundColor = "red";
}
</script>
<div style="height:2000px;">
Scroll the page down. The page will turn red when the scrolling has finished.
</div>
</body>
</html>
Check out this example:
https://codepen.io/len0xx/pen/JjadOgR
const toolbar = document.querySelector('.mobile-toolbar')
const mobileToolbarTop = (toolbar.offsetTop) + 50
let previousScroll = 0
let previousTimeout = 0
window.addEventListener('scroll', () => {
const currentScroll = window.scrollY
if (currentScroll > mobileToolbarTop) {
if (currentScroll > previousScroll) {
toolbar.classList.add('mobile-toolbar__hidden')
toolbar.classList.remove('mobile-toolbar--fixed')
}
else {
toolbar.classList.remove('mobile-toolbar__hidden')
toolbar.classList.add('mobile-toolbar--fixed')
}
}
if (previousTimeout) {
clearTimeout(previousTimeout)
}
previousTimeout = setTimeout(() => {
const newScroll = window.scrollY
if (newScroll <= currentScroll) {
toolbar.classList.remove('mobile-toolbar__hidden')
toolbar.classList.add('mobile-toolbar--fixed')
}
}, 300)
previousScroll = currentScroll
})
So I am trying to use the JavaScript on scroll to call a function. But I wanted to know if I could detect the direction of the the scroll without using jQuery. If not then are there any workarounds?
I was thinking of just putting a 'to top' button but would like to avoid that if I could.
I have now just tried using this code but it didn't work:
if document.body.scrollTop <= 0 {
alert ("scrolling down")
} else {
alert ("scrolling up")
}
It can be detected by storing the previous scrollTop value and comparing the current scrollTop value with it.
JavaScript :
var lastScrollTop = 0;
// element should be replaced with the actual target element on which you have applied scroll, use window in case of no target element.
element.addEventListener("scroll", function(){ // or window.addEventListener("scroll"....
var st = window.pageYOffset || document.documentElement.scrollTop; // Credits: "https://github.com/qeremy/so/blob/master/so.dom.js#L426"
if (st > lastScrollTop) {
// downscroll code
} else if (st < lastScrollTop) {
// upscroll code
} // else was horizontal scroll
lastScrollTop = st <= 0 ? 0 : st; // For Mobile or negative scrolling
}, false);
Simple way to catch all scroll events (touch and wheel)
window.onscroll = function(e) {
// print "false" if direction is down and "true" if up
console.log(this.oldScroll > this.scrollY);
this.oldScroll = this.scrollY;
}
Use this to find the scroll direction. This is only to find the direction of the Vertical Scroll. Supports all cross browsers.
var scrollableElement = document.body; //document.getElementById('scrollableElement');
scrollableElement.addEventListener('wheel', checkScrollDirection);
function checkScrollDirection(event) {
if (checkScrollDirectionIsUp(event)) {
console.log('UP');
} else {
console.log('Down');
}
}
function checkScrollDirectionIsUp(event) {
if (event.wheelDelta) {
return event.wheelDelta > 0;
}
return event.deltaY < 0;
}
Example
You can try doing this.
function scrollDetect(){
var lastScroll = 0;
window.onscroll = function() {
let currentScroll = document.documentElement.scrollTop || document.body.scrollTop; // Get Current Scroll Value
if (currentScroll > 0 && lastScroll <= currentScroll){
lastScroll = currentScroll;
document.getElementById("scrollLoc").innerHTML = "Scrolling DOWN";
}else{
lastScroll = currentScroll;
document.getElementById("scrollLoc").innerHTML = "Scrolling UP";
}
};
}
scrollDetect();
html,body{
height:100%;
width:100%;
margin:0;
padding:0;
}
.cont{
height:100%;
width:100%;
}
.item{
margin:0;
padding:0;
height:100%;
width:100%;
background: #ffad33;
}
.red{
background: red;
}
p{
position:fixed;
font-size:25px;
top:5%;
left:5%;
}
<div class="cont">
<div class="item"></div>
<div class="item red"></div>
<p id="scrollLoc">0</p>
</div>
Initialize an oldValue
Get the newValue by listening to the event
Subtract the two
Conclude from the result
Update oldValue with the newValue
// Initialization
let oldValue = 0;
//Listening on the event
window.addEventListener('scroll', function(e){
// Get the new Value
newValue = window.pageYOffset;
//Subtract the two and conclude
if(oldValue - newValue < 0){
console.log("Up");
} else if(oldValue - newValue > 0){
console.log("Down");
}
// Update the old value
oldValue = newValue;
});
This is an addition to what prateek has answered.There seems to be a glitch in the code in IE so i decided to modify it a bit nothing fancy(just another condition)
$('document').ready(function() {
var lastScrollTop = 0;
$(window).scroll(function(event){
var st = $(this).scrollTop();
if (st > lastScrollTop){
console.log("down")
}
else if(st == lastScrollTop)
{
//do nothing
//In IE this is an important condition because there seems to be some instances where the last scrollTop is equal to the new one
}
else {
console.log("up")
}
lastScrollTop = st;
});});
While the accepted answer works, it is worth noting that this will fire at a high rate. This can cause performance issues for computationally expensive operations.
The recommendation from MDN is to throttle the events. Below is a modification of their sample, enhanced to detect scroll direction.
Modified from: https://developer.mozilla.org/en-US/docs/Web/API/Document/scroll_event
// ## function declaration
function scrollEventThrottle(fn) {
let last_known_scroll_position = 0;
let ticking = false;
window.addEventListener("scroll", function () {
let previous_known_scroll_position = last_known_scroll_position;
last_known_scroll_position = window.scrollY;
if (!ticking) {
window.requestAnimationFrame(function () {
fn(last_known_scroll_position, previous_known_scroll_position);
ticking = false;
});
ticking = true;
}
});
}
// ## function invocation
scrollEventThrottle((scrollPos, previousScrollPos) => {
if (previousScrollPos > scrollPos) {
console.log("going up");
} else {
console.log("going down");
}
});
This simple code would work: Check the console for results.
let scroll_position = 0;
let scroll_direction;
window.addEventListener('scroll', function(e){
scroll_direction = (document.body.getBoundingClientRect()).top > scroll_position ? 'up' : 'down';
scroll_position = (document.body.getBoundingClientRect()).top;
console.log(scroll_direction);
});
You can get the scrollbar position using document.documentElement.scrollTop. And then it is simply matter of comparing it to the previous position.
If anyone looking to achieve it with React hooks
const [scrollStatus, setScrollStatus] = useState({
scrollDirection: null,
scrollPos: 0,
});
useEffect(() => {
window.addEventListener("scroll", handleScrollDocument);
return () => window.removeEventListener("scroll", handleScrollDocument);
}, []);
function handleScrollDocument() {
setScrollStatus((prev) => { // to get 'previous' value of state
return {
scrollDirection:
document.body.getBoundingClientRect().top > prev.scrollPos
? "up"
: "down",
scrollPos: document.body.getBoundingClientRect().top,
};
});
}
console.log(scrollStatus.scrollDirection)
I personally use this code to detect scroll direction in javascript...
Just you have to define a variable to store lastscrollvalue and then use this if&else
let lastscrollvalue;
function headeronscroll() {
// document on which scroll event will occur
var a = document.querySelector('.refcontainer');
if (lastscrollvalue == undefined) {
lastscrollvalue = a.scrollTop;
// sets lastscrollvalue
} else if (a.scrollTop > lastscrollvalue) {
// downscroll rules will be here
lastscrollvalue = a.scrollTop;
} else if (a.scrollTop < lastscrollvalue) {
// upscroll rules will be here
lastscrollvalue = a.scrollTop;
}
}
Modifying Prateek's answer, if there is no change in lastScrollTop, then it would be a horizontal scroll (with overflow in the x direction, can be used by using horizontal scrollbars with a mouse or using scrollwheel + shift.
const containerElm = document.getElementById("container");
let lastScrollTop = containerElm.scrollTop;
containerElm.addEventListener("scroll", (evt) => {
const st = containerElm.scrollTop;
if (st > lastScrollTop) {
console.log("down scroll");
} else if (st < lastScrollTop) {
console.log("up scroll");
} else {
console.log("horizontal scroll");
}
lastScrollTop = Math.max(st, 0); // For mobile or negative scrolling
});
This seems to be working fine.
document.addEventListener('DOMContentLoaded', () => {
var scrollDirectionDown;
scrollDirectionDown = true;
window.addEventListener('scroll', () => {
if (this.oldScroll > this.scrollY) {
scrollDirectionDown = false;
} else {
scrollDirectionDown = true;
}
this.oldScroll = this.scrollY;
// test
if (scrollDirectionDown) {
console.log('scrolling down');
} else {
console.log('scrolling up');
}
});
});
Sometimes there are inconsistencies in scrolling behavior which does not properly update the scrollTop attribute of an element. It would be safer to put some threshold value before deciding the scroll direction.
let lastScroll = 0
let threshold = 10 // must scroll by 10 units to know the direction of scrolling
element.addEventListener("scroll", () => {
let newScroll = element.scrollTop
if (newScroll - lastScroll > threshold) {
// "up" code here
} else if (newScroll - lastScroll < -threshold) {
// "down" code here
}
lastScroll = newScroll
})
let arrayScroll = [];
window.addEventListener('scroll', ()=>{
arrayScroll.splice(1); //deleting unnecessary data so that array does not get too big
arrayScroll.unshift(Math.round(window.scrollY));
if(arrayScroll[0] > arrayScroll[1]){
console.log('scrolling down');
} else{
console.log('scrolling up');
}
})
I have self-made the above solution. I am not sure if this solution may cause any considerable performance issue comparing other solutions as I have just started learning JS and not yet have completed my begginer course. Any suggestion or advice from experienced coder is highly appriciated. ThankYou!
I am not a javascript expert. I have these two codes that don't work simultaneously. I don't know why and i ask you where could be the issue?
// This is the first part
//Get the button
var mybutton = document.getElementById("scrollToTop");
// 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 > 200 || document.documentElement.scrollTop > 200) {
mybutton.style.display = "block";
} else {
mybutton.style.display = "none";
}
}
// When the user clicks on the button, scroll to the top of the document
function toTopFunction() {
document.body.scrollTop = 0;
document.documentElement.scrollTop = 0;
}
// When the user scrolls the page, execute myFunction
window.onscroll = function() {
myFunction()
};
// This is the second part
function myFunction() {
var winScroll = document.body.scrollTop || document.documentElement.scrollTop;
var height = document.documentElement.scrollHeight - document.documentElement.clientHeight;
var scrolled = (winScroll / height) * 100;
document.getElementById("myBar").style.width = scrolled + "%";
}
Thanks to anyone
Every time you assign to window.onscroll it replaces the previous assignment.
If you want multiple event listeners, use addEventListener().
window.addEventListener("scroll", scrollFunction);
window.addEventListener("scroll", myFunction);
or call both functions in a single handler:
window.onscroll = function() {
scrollFunction();
myFunction();
};
I have been trying to make a simple "smoothscroll" function using location.href that triggers on the mousewheel. The main problem is that the EventListener(wheel..) gets a bunch of inputs over the span of ca. 0,9 seconds which keeps triggering the function. "I only want the function to run once".
In the code below I have tried to remove the eventlistener as soon as the function runs, which actually kinda work, the problem is that I want it to be added again, hence the timed function at the bottom. This also kinda work but I dont want to wait a full second to be able to scroll and if I set it to anything lover the function will run multiple times.
I've also tried doing it with conditions "the commented out true or false variables" which works perfectly aslong as you are only scrolling up and down but you cant scroll twice or down twice.
window.addEventListener('wheel', scrolltest, true);
function scrolltest(event) {
window.removeEventListener('wheel', scrolltest, true);
i = event.deltaY;
console.log(i);
if (webstate == 0) {
if (i < 0 && !upexecuted) {
// upexecuted = true;
location.href = "#forside";
// downexecuted = false;
} else if (i > 0 && !downexecuted) {
// downexecuted = true;
location.href = "#underside";
// upexecuted = false;
}
}
setTimeout(function(){ window.addEventListener('wheel', scrolltest, true); }, 1000);
}
I had hoped there was a way to stop the wheel from constantly produce inputs over atleast 0.9 seconds.
"note: don't know if it can help in some way but when the browser is not clicked (the active window) the wheel will registre only one value a nice 100 for down and -100 for up"
What you're trying to do is called "debouncing" or "throttling". (Those aren't exactly the same thing, but you can look up the difference in case it's going to matter to you.) Functions for this are built into libraries like lodash, but if using a library like that is too non-vanilla for what you have in mind, you can always define your own debounce function: https://www.geeksforgeeks.org/debouncing-in-javascript/
You might also want to look into requestanimationframe.
a different approach
okey after fiddeling with this for just about 2 days i got fustrated and started over. no matter what i did the browsers integrated "glide-scroll" was messing up the event trigger. anyway i decided to animate the scrolling myself and honestly it works better than i had imagined: here is my code if anyone want to do this:
var body = document.getElementsByTagName("BODY")[0];
var p1 = document.getElementById('page1');
var p2 = document.getElementById('page2');
var p3 = document.getElementById('page3');
var p4 = document.getElementById('page4');
var p5 = document.getElementById('page5');
var whatpage = 1;
var snap = 50;
var i = 0;
// this part is really just to read what "page" you are on if you update the site. if you add more pages you should remember to add it here too.
window.onload = setcurrentpage;
function setcurrentpage() {
if (window.pageYOffset == p1.offsetTop) {
whatpage = 1;
} else if (window.pageYOffset == p2.offsetTop) {
whatpage = 2;
} else if (window.pageYOffset == p3.offsetTop) {
whatpage = 3;
} else if (window.pageYOffset == p4.offsetTop) {
whatpage = 4;
} else if (window.pageYOffset == p5.offsetTop) {
whatpage = 5;
}
}
// this code is designet to automaticly work with any "id" you have aslong as you give it a variable called p"number" fx p10 as seen above.
function smoothscroll() {
var whatpagenext = whatpage+1;
var whatpageprev = whatpage-1;
var currentpage = window['p'+whatpage];
var nextpage = window['p'+whatpagenext];
var prevpage = window['p'+whatpageprev];
console.log(currentpage);
if (window.pageYOffset > currentpage.offsetTop + snap && window.pageYOffset < nextpage.offsetTop - snap){
body.style.overflowY = "hidden";
i++
window.scrollTo(0, window.pageYOffset+i);
if (window.pageYOffset <= nextpage.offsetTop + snap && window.pageYOffset >= nextpage.offsetTop - snap) {
i=0;
window.scrollTo(0, nextpage.offsetTop);
whatpage += 1;
body.style.overflowY = "initial";
}
} else if (window.pageYOffset < currentpage.offsetTop - snap && window.pageYOffset > prevpage.offsetTop + snap){
body.style.overflowY = "hidden";
i--
window.scrollTo(0, window.pageYOffset+i);
if (window.pageYOffset >= prevpage.offsetTop - snap && window.pageYOffset <= prevpage.offsetTop + snap) {
i=0;
window.scrollTo(0, prevpage.offsetTop);
whatpage -= 1;
body.style.overflowY = "initial";
}
}
}
to remove the scrollbar completely just add this to your stylesheet:
::-webkit-scrollbar {
width: 0px;
background: transparent;
}
With my current code I can only have one or the other, which is either my sticky navigation or a back to top button that appears at a 100px from the top of the document. Is there any way I can use both?
This is my current code
window.onscroll = function() {navFunction()};
var navbar = document.getElementById("navbar");
var sticky = navbar.offsetTop;
function navFunction() {
if (window.pageYOffset >= sticky) {
navbar.classList.add("sticky")
} else {
navbar.classList.remove("sticky");
}
and
window.onscroll = function() {scrollFunction()};
function scrollFunction() {
if (document.body.scrollTop > 100 || document.documentElement.scrollTop > 100) {
document.getElementById("myBtn").style.display = "block";
} else {
document.getElementById("myBtn").style.display = "none";
}
}
function topFunction() {
document.body.scrollTop = 0; // For Safari
document.documentElement.scrollTop = 0; // For Chrome, Firefox, IE and Opera
}
sorry if this is a silly question. I am still new to this :)
Thanks in advance!
You can call both functions inside window.onscroll anonymous function:
window.onscroll = function() {
navFunction();
scrollFunction();
};
Alternatively, you can use the standard addEventListener method to register both functions:
window.addEventListener("scroll", navFunction);
window.addEventListener("scroll", scrollFunction);
Notice that in this way we don't use the parentheses with the two functions because we're not executing them. We're just telling the event listener the name of the function that it will execute when the event occurs.
One thing you can do is just reorganize your code to call both functions.
// Define the functions and the variables you need first here
// function topFunction() {...} etc
// call both functions inside the scroll event here.
window.onscroll = function() {
scrollFunction();
navFunction()
};
The other way to run multiple functions on an event is by using addEventListener()
window.addEventListener("scroll",scrollFunction,false);
window.addEventListener("scroll",navFunction,false);
You can keep appending as many functions as you want, though you risk making your web page slower.
window.onscroll = function() {onscroll_function()};
var navbar = document.getElementById("navbar");
var sticky = navbar.offsetTop;
function onscroll_function() {
navFunction();
scrollFunction();
//...what ever else you want to trigger
}
function navFunction() {
if (window.pageYOffset >= sticky) {
navbar.classList.add("sticky")
} else {
navbar.classList.remove("sticky");
}
}
function scrollFunction() {
if (document.body.scrollTop > 100 || document.documentElement.scrollTop > 100) {
document.getElementById("myBtn").style.display = "block";
} else {
document.getElementById("myBtn").style.display = "none";
}
}
function topFunction() {
document.body.scrollTop = 0; // For Safari
document.documentElement.scrollTop = 0; // For Chrome, Firefox, IE and Opera
}