I have a webpage that when scrolled down, the text freezes when it reaches the last paragraph of text but the images keep on scrolling. I've got the implementation working but there is a lot of jank when scrolling with a mouse wheel, not so much if I click and drag the scroll bar.
Are there any optimizations I can make to this code to make work as intended or is there a different way to accomplish the same task?
window.addEventListener('scroll', function (e) {
window.requestAnimationFrame(keepTextStationary);
//keepTextStationary(); // Less janky, but still horrible
});
function keepTextStationary() {
var textRect = writtenContent.getBoundingClientRect();
var imageRec = images.getBoundingClientRect();
if (textRect.bottom < window.innerHeight && document.documentElement.scrollTop > 0) {
writtenContent.style.position = 'relative';
writtenContent.style.bottom = (225 - document.documentElement.scrollTop) + 'px';
if (imagesTop === undefined) {
imagesTop = imageRec.y;
}
} else {
writtenContent.style.bottom = (225 - document.documentElement.scrollTop) + 'px';
}
if (imageRec.y >= imagesTop) {
writtenContent.style.position = '';
}
}
Here is the site so you can see the problem.
https://bowerbankninow.azurewebsites.net/exhibitions/oscar-perry-the-pheasant
You are causing layout trashing every time you call getBoundingClientRect. Try debouncing your scroll events:
var lastScrollY = 0;
var ticking = false;
function keepTextStationary() {
var textRect = writtenContent.getBoundingClientRect();
var imageRec = images.getBoundingClientRect();
if (textRect.bottom < window.innerHeight && lastScrollY > 0) {
writtenContent.style.position = 'relative';
writtenContent.style.bottom = (225 - lastScrollY) + 'px';
if (imagesTop === undefined) {
imagesTop = imageRec.y;
}
} else {
writtenContent.style.bottom = (225 - lastScrollY) + 'px';
}
if (imageRec.y >= imagesTop) {
writtenContent.style.position = '';
}
ticking = false;
}
function onScroll() {
lastScrollY = document.documentElement.scrollTop;
requestTick();
}
function requestTick() {
if (!ticking) {
requestAnimationFrame(keepTextStationary);
ticking = true;
}
}
window.addEventListener('scroll', onScroll );
See this article for in-depth explanation: https://www.html5rocks.com/en/tutorials/speed/animations/
You dont.
Relocations / styling in javascript take place after the CSS has been loaded. Bad practise. What you can do, is make it animated to make it look less horrible.
Why is pure CSS not an option ?
So I'm using mousewheel.js to handle mousewheel scrolling in any part of the document so I can scroll a custom scroller made by Nicescroll.
You can check a fiddle of it working here
Here's part of the code that handles the scrolling:
function activate_mousewheel()
{
$(document).bind('mousewheel', function(event, delta, deltaX, deltaY)
{
if(delta < 0)
{
console.log(1);
$('#postscroller').scrollTop($('#postscroller').scrollTop() + 60);
}
else
{
console.log(2);
$('#postscroller').scrollTop($('#postscroller').scrollTop() - 60);
}
});
}
Now my problem is that when this is used in a computer with a touchpad with horizontal scrolling enabled the movement is all jittery rendering it unusable. So this problem will affect people using any kind of laptop with horizontal scrolling like a chromebook or a macbook.
I've tried doing various fixes, playing with the deltas but to no avail.
I was hoping someone here could find a solution.
Thanks.
I had to find a solution for the problem myself, and after hours of trying and beeing creative here is what i came up with. Of course you have to modify it to integrate it to work smoothly with nicescroll etc. as this is plain JS:
Well I needed to get a solution. So I found a acceptable solution for this problem:
var scrolling = false;
var oldTime = 0;
var newTime = 0;
var isTouchPad;
var eventCount = 0;
var eventCountStart;
var mouseHandle = function (evt) {
var isTouchPadDefined = isTouchPad || typeof isTouchPad !== "undefined";
console.log(isTouchPadDefined);
if (!isTouchPadDefined) {
if (eventCount === 0) {
eventCountStart = new Date().getTime();
}
eventCount++;
if (new Date().getTime() - eventCountStart > 50) {
if (eventCount > 5) {
isTouchPad = true;
} else {
isTouchPad = false;
}
isTouchPadDefined = true;
}
}
if (isTouchPadDefined) {
// here you can do what you want
// i just wanted the direction, for swiping, so i have to prevent
// the multiple event calls to trigger multiple unwanted actions (trackpad)
if (!evt) evt = event;
var direction = (evt.detail<0 || evt.wheelDelta>0) ? 1 : -1;
if (isTouchPad) {
newTime = new Date().getTime();
if (!scrolling && newTime-oldTime > 550 ) {
scrolling = true;
if (direction < 0) {
// swipe down
} else {
// swipe up
}
setTimeout(function() {oldTime = new Date().getTime();scrolling = false}, 500);
}
} else {
if (direction < 0) {
// swipe down
} else {
// swipe up
}
}
}
}
And registering the events:
document.addEventListener("mousewheel", mouseHandle, false);
document.addEventListener("DOMMouseScroll", mouseHandle, false);
Here is how it works:
When the user first scrolls, it will detect and check that in 50ms not more than 5 events got triggered, which is pretty unusual for a normal mouse, but not for a trackpad.
Then there is the else part, which is not for importance for the detection, but rather a trick to call a function once like when a user swipes. Please come at me if I wasn't clear enough, it was very tricky to get this working, and is of course a less than ideal workaround.
Edit: I optimized the code now as much as I can. It detects the mouseroll on the second time and swipe on trackpad instantly. Removed also a lot of repeating and unnecessary code.
The mousewheel event fires a lot of times. So to regulate the event, so it doesn't fire as much, use a throttle function.
https://lodash.com/docs#throttle
Because the event will not fire as often, the performance should be better.
function onMouseWheel(event, delta, deltaX, deltaY)
{
if(delta < 0)
{
console.log(1);
$('#postscroller').scrollTop($('#postscroller').scrollTop() + 60);
}
else
{
console.log(2);
$('#postscroller').scrollTop($('#postscroller').scrollTop() - 60);
}
});
function activate_mousewheel()
{
$(document).bind('mousewheel', _.throttle(onMouseWheel, 100);
}
I have a div, with a scroll bar, When it reaches the end, my page starts scrolling. Is there anyway I can stop this behavior ?
You can inactivate the scrolling of the whole page by doing something like this:
<div onmouseover="document.body.style.overflow='hidden';" onmouseout="document.body.style.overflow='auto';"></div>
Found the solution.
http://jsbin.com/itajok
This is what I needed.
And this is the code.
http://jsbin.com/itajok/edit#javascript,html
Uses a jQuery Plug-in.
Update due to deprecation notice
From jquery-mousewheel:
The old behavior of adding three arguments (delta, deltaX, and deltaY)
to the event handler is now deprecated and will be removed in later
releases.
Then, event.deltaY must now be used:
var toolbox = $('#toolbox'),
height = toolbox.height(),
scrollHeight = toolbox.get(0).scrollHeight;
toolbox.off("mousewheel").on("mousewheel", function (event) {
var blockScrolling = this.scrollTop === scrollHeight - height && event.deltaY < 0 || this.scrollTop === 0 && event.deltaY > 0;
return !blockScrolling;
});
Demo
The selected solution is a work of art. Thought it was worthy of a plugin....
$.fn.scrollGuard = function() {
return this
.on( 'wheel', function ( e ) {
var event = e.originalEvent;
var d = event.wheelDelta || -event.detail;
this.scrollTop += ( d < 0 ? 1 : -1 ) * 30;
e.preventDefault();
});
};
This has been an ongoing inconvenience for me and this solution is so clean compared to other hacks I've seen. Curious to know how more about how it works and how widely supported it would be, but cheers to Jeevan and whoever originally came up with this. BTW - stackoverflow answer editor needs this!
UPDATE
I believe this is better in that it doesn't try to manipulate the DOM at all, only prevents bubbling conditionally...
$.fn.scrollGuard2 = function() {
return this
.on( 'wheel', function ( e ) {
var $this = $(this);
if (e.originalEvent.deltaY < 0) {
/* scrolling up */
return ($this.scrollTop() > 0);
} else {
/* scrolling down */
return ($this.scrollTop() + $this.innerHeight() < $this[0].scrollHeight);
}
})
;
};
Works great in chrome and much simpler than other solutions... let me know how it fares elsewhere...
FIDDLE
You could use a mouseover event on the div to disable the body scrollbar and then a mouseout event to activate it again?
E.g. The HTML
<div onmouseover="disableBodyScroll();" onmouseout="enableBodyScroll();">
content
</div>
And then the javascript like so:
var body = document.getElementsByTagName('body')[0];
function disableBodyScroll() {
body.style.overflowY = 'hidden';
}
function enableBodyScroll() {
body.style.overflowY = 'auto';
}
As answered here, most modern browsers now support the overscroll-behavior: none; CSS property, that prevents scroll chaining. And that's it, just one line!
Here's a cross-browser way to do this on the Y axis, it works on desktop and mobile. Tested on OSX and iOS.
var scrollArea = this.querySelector(".scroll-area");
scrollArea.addEventListener("wheel", function() {
var scrollTop = this.scrollTop;
var maxScroll = this.scrollHeight - this.offsetHeight;
var deltaY = event.deltaY;
if ( (scrollTop >= maxScroll && deltaY > 0) || (scrollTop === 0 && deltaY < 0) ) {
event.preventDefault();
}
}, {passive:false});
scrollArea.addEventListener("touchstart", function(event) {
this.previousClientY = event.touches[0].clientY;
}, {passive:false});
scrollArea.addEventListener("touchmove", function(event) {
var scrollTop = this.scrollTop;
var maxScroll = this.scrollHeight - this.offsetHeight;
var currentClientY = event.touches[0].clientY;
var deltaY = this.previousClientY - currentClientY;
if ( (scrollTop >= maxScroll && deltaY > 0) || (scrollTop === 0 && deltaY < 0) ) {
event.preventDefault();
}
this.previousClientY = currentClientY;
}, {passive:false});
I wrote resolving for this issue
var div;
div = document.getElementsByClassName('selector')[0];
div.addEventListener('mousewheel', function(e) {
if (div.clientHeight + div.scrollTop + e.deltaY >= div.scrollHeight) {
e.preventDefault();
div.scrollTop = div.scrollHeight;
} else if (div.scrollTop + e.deltaY <= 0) {
e.preventDefault();
div.scrollTop = 0;
}
}, false);
If I understand your question correctly, then you want to prevent scrolling of the main content when the mouse is over a div (let's say a sidebar). For that, the sidebar may not be a child of the scrolling container of the main content (which was the browser window), to prevent the scroll event from bubbling up to its parent.
This possibly requires some markup changes in the following manner:
<div id="wrapper">
<div id="content">
</div>
</div>
<div id="sidebar">
</div>
See it's working in this sample fiddle and compare that with this sample fiddle which has a slightly different mouse leave behavior of the sidebar.
See also scroll only one particular div with browser's main scrollbar.
this disables the scrolling on the window if you enter the selector element.
works like charms.
elements = $(".selector");
elements.on('mouseenter', function() {
window.currentScrollTop = $(window).scrollTop();
window.currentScrollLeft = $(window).scrollTop();
$(window).on("scroll.prevent", function() {
$(window).scrollTop(window.currentScrollTop);
$(window).scrollLeft(window.currentScrollLeft);
});
});
elements.on('mouseleave', function() {
$(window).off("scroll.prevent");
});
You can inactivate the scrolling of the whole page by doing something like this but display the scrollbar!
<div onmouseover="document.body.style.overflow='hidden'; document.body.style.position='fixed';" onmouseout="document.body.style.overflow='auto'; document.body.style.position='relative';"></div>
$this.find('.scrollingDiv').on('mousewheel DOMMouseScroll', function (e) {
var delta = -e.originalEvent.wheelDelta || e.originalEvent.detail;
var scrollTop = this.scrollTop;
if((delta < 0 && scrollTop === 0) || (delta > 0 && this.scrollHeight - this.clientHeight - scrollTop === 0)) {
e.preventDefault();
}
});
Based on ceed's answer, here is a version that allows nesting scroll guarded elements. Only the element the mouse is over will scroll, and it scrolls quite smoothly. This version is also re-entrant. It can be used multiple times on the same element and will correctly remove and reinstall the handlers.
jQuery.fn.scrollGuard = function() {
this
.addClass('scroll-guarding')
.off('.scrollGuard').on('mouseenter.scrollGuard', function() {
var $g = $(this).parent().closest('.scroll-guarding');
$g = $g.length ? $g : $(window);
$g[0].myCst = $g.scrollTop();
$g[0].myCsl = $g.scrollLeft();
$g.off("scroll.prevent").on("scroll.prevent", function() {
$g.scrollTop($g[0].myCst);
$g.scrollLeft($g[0].myCsl);
});
})
.on('mouseleave.scrollGuard', function() {
var $g = $(this).parent().closest('.scroll-guarding');
$g = $g.length ? $g : $(window);
$g.off("scroll.prevent");
});
};
One easy way to use is to add a class, such as scroll-guard, to all the elements in the page that you allow scrolling on. Then use $('.scroll-guard').scrollGuard() to guard them.
If you apply an overflow: hidden style it should go away
edit: actually I read your question wrong, that will only hide the scroll bar but I don't think that's what you are looking for.
I couldn't get any of the answers to work in Chrome and Firefox, so I came up with this amalgamation:
$someElement.on('mousewheel DOMMouseScroll', scrollProtection);
function scrollProtection(event) {
var $this = $(this);
event = event.originalEvent;
var direction = (event.wheelDelta * -1) || (event.detail);
if (direction < 0) {
if ($this.scrollTop() <= 0) {
return false;
}
} else {
if ($this.scrollTop() + $this.innerHeight() >= $this[0].scrollHeight) {
return false;
}
}
}
http://jsfiddle.net/nicktheandroid/tfZns/4/
You grab the page and fling it up or down, kind of like an android or iphone. It works in Chrome and Safari (webkit) but it does not work in firefox, ie9 or Opera.
I got help with some of this script, and i'm really not sure what's wrong for it not to work in those browsers. I thought something in Javascript/Jquery would work the same in pretty much every browser, guess I was wrong.
In Webkit browsers you can mousedown on the page, then flick up or down and release the mouse button and the page will scroll/slide, like how you flick or drag your finger across a touchscreen phone and it scrolls the browser page up or down. In Firefox, IE9, and Opera, trying to mousedown, then flick/drag only results in the numbers on the page being highlighted, the page doesn't scroll like it should.
Javascript:
var gesturesX = 0;
var gesturesY = 0;
var startPosition = 0;
var velocity = 0;
var isMouseDown = false;
var startScrollTop = 0;
var timer;
function GetVelocity() {
velocity = startPosition - gesturesY;
}
$(document).mousemove(function(e) {
gesturesX = parseInt(e.pageX, 10);
gesturesY = parseInt(e.pageY, 10);
$("#mouse").html(gesturesY);
if (isMouseDown) {
var scrollToPosition = startScrollTop + (startPosition - gesturesY);
$("body").scrollTop(scrollToPosition);
return false;
}
});
$(document).mousedown(function() {
if ($("body").is(':animated')) {
$("body").stop(true, false).trigger('mouseup');
}
startPosition = gesturesY;
startScrollTop = $("body").scrollTop();
isMouseDown = true;
timer = window.setTimeout(GetVelocity, 50);
$(document).everyTime(50, function(i) {
velocity = startPosition - gesturesY;
});
});
$(document).mouseup(function() {
isMouseDown = false;
if (velocity !== 0) {
$Body = $("body");
var distance = velocity * 10;
var scrollToPosition = $Body.scrollTop() + distance;
$Body.eq(0).stop().animate({
scrollTop: scrollToPosition
}, 1000);
velocity = 0;
}
return false;
});
// create a ton of numbers to make the page long - below
$("#test p").each(function(index) {
$(this).prepend('<span class="commentnumber">' + index + 1 + '</span>');
});
Change "body" to "html" and it'll work. Tested on newest Firefox and Opera, you'll have to check if it works on older versions.
$("html").scrollTop(scrollToPosition);
You can also consider disabling text selection because it looks a little funny when you scroll the page.
I think you should use selector $('html, body')
I want to drag an element named moveMe and drop it anywhere within the window. This code already works on google chrome using a desktop computer. But when i opened this file in an iPad, it is not functioning. I had researched about ontouchstart, ontouchmove and ontouchend and applied it to this code but still it doesn't work. Please help me on how to get this code work on an iPad without using jQuery because iPad is not good at handling jQuery. And if there is a more efficient way to do this.
function init() {
movMeId=document.getElementById("moveMe");
movMeId.style.left="900px";
movMeId.style.top="500px";
}
document.onmousedown=coordinates;
document.onmouseup=mouseup;
function coordinates(e) {
if (!e) {
e = window.event;
}
var sender = (typeof( window.event ) != "undefined" ) ? e.srcElement : e.target;
if (sender.id == "moveMe") {
mouseover=true;
pleft = parseInt(movMeId.style.left);
ptop = parseInt(movMeId.style.top);
xcoor = e.clientX;
ycoor = e.clientY;
document.onmousemove = moveImage;
return false;
}
else {
return false;
}
}
function moveImage(e) {
if (!e) {
e = window.event;}
movMeId.style.left = pleft + e.clientX - xcoor + "px";
movMeId.style.top = ptop + e.clientY - xcoor + "px";
return false;
}
function mouseup(e) {
document.onmousemove=null;
movMeId.style.left="900px";
movMeId.style.top="500px";
}
You might find this answer about HTML5 Drag and Drop API on Touch Screen Devices useful: HTML5 Drag and Drop API on Touch Screen Devices