How to disable scrolling in outer elements? - javascript

I have a vertically-scrolling div within a page that also scrolls vertically.
When the child div is scrolled with the mouse wheel and reaches the top or bottom of the scroll bar, the page (body) begins to scroll. While the mouse is over the child div, I'd like the page (body) scroll to be locked.
This SO post (scroll down to the selected answer) demonstrates the problem well.
This SO question is essentially the same as mine, but the selected answer causes my page contents to noticeably shift horizontally as the scrollbar disappears and reappears.
I thought there might be a solution that leverages event.stopPropagation(), but couldn't get anything to work. In ActionScript, this kind of thing would be solved by placing a mousewheel handler on the child div that calls stopPropagation() on the event before it reaches the body element. Since JS and AS are both ECMAScript languages, I thought the concept might translate, but it didn't seem to work.
Is there a solution that keeps my page contents from shifting around? Most likely using stopPropagation rather than a CSS fix? JQuery answers are welcome as is pure JS.

here's what i ended up with. very similar to #mrtsherman's answer here, only pure JS events instead of jQuery. i still used jQuery for selecting and moving the child div around, though.
// earlier, i have code that references my child div, as childDiv
function disableWindowScroll () {
if (window.addEventListener) {
window.addEventListener("DOMMouseScroll", onChildMouseWheel, false);
}
window.onmousewheel = document.onmousewheel = onChildMouseWheel;
}
function enableWindowScroll () {
if (window.removeEventListener) {
window.removeEventListener("DOMMouseScroll", onArticleMouseWheel, false);
}
window.onmousewheel = document.onmousewheel = null;
}
function onChildMouseWheel (event) {
var scrollTgt = 0;
event = window.event || event;
if (event.detail) {
scrollTgt = -40 * event.detail;
} else {
scrollTgt = event.wheelDeltaY;
}
if (scrollTgt) {
preventDefault(event);
$(childDiv).scrollTop($(childDiv).scrollTop() - scrollTgt);
}
}
function preventDefault (event) {
event = event || window.event;
if (event.preventDefault) {
event.preventDefault();
}
event.returnValue = false;
}
i've noticed the scrolling doesn't match normal scrolling exactly; it seems to scroll a bit faster than without this code. i assume i can fix by knocking down wheelDeltaY a bit, but it's odd that it would be reported differently by javascript than it's actually implemented by the browser...

I usually do it with a small hack listening to the scroll event on the document: it resets the scroll height back to the original one - effectively freezing the document from scrolling but any inner element with overflow: auto will still scroll nicely:
var scrollTop = $(document).scrollTop();
$(document).on('scroll.scrollLock', function() {
$(document).scrollTop(scrollTop);
});
and then when I'm done with the inner scroll lock:
$(document).off('scroll.scrollLock');
the .scrollLock event namespace makes sure I'm not messing with any other event listeners on scroll.

Although this is an old question, here is how I do it with jQuery. This allows you to scroll a list within an outer list, or you can change the outer list to the document to do what the OP asked.
window.scrollLockHolder = null;
function lockScroll(id){
if (window.scrollLockHolder == null){
window.scrollLockHolder = $('#' + id).scrollTop();
}
$('#' + id).on('scroll', function(){
$('#' + id).scrollTop(window.scrollLockHolder);
});
}
function unlockScroll(id){
$('#' + id).off('scroll');
window.scrollLockHolder = null;
}
And you can use it like this:
<ul onmousemove="lockScroll('outer-scroller-id')" onmouseout="unlockScroll('outer-scroller-id')">
<li>...</li>
<li>...</li>
</ul>

what about this:
div.onmousemove = function() { // may be onmouseover also works fine
document.body.style.overflow = "hidden";
document.documentElement.style.overflow = "hidden";
};
div.onmouseout = function() {
document.body.style.overflow = "auto";
document.documentElement.style.overflow = "auto";
};

Related

jQuery infinite scrolling scrolling in fixed div

Background
I am trying to create an infinite scrolling table inside a fixed position div. The problem is that all the solutions I come across use the window height and document scrollTop to calculate if the user has scrolled to the bottom of the screen.
Problem
I have tried to create a jQuery plugin that can calculate if a user has scrolled to the bottom of a fixed div with overflow: scroll; set.
My approach has been to create a wrapper div (the div with a fixed position and overflow: scroll) that wraps the table, I also place another div at the bottom of the table. I then try calculate if the wrapper.scrollTop() is greater than the bottom div position.top every time the wrapper is scrolled. I then load the new records and append them to the table body.
$.fn.isScrolledTo = function () {
var element = $(this);
var bottom = element.find('.bottom');
$(element).scroll(function () {
if (element.scrollTop() >= bottom.position().top) {
var tableBody = element.find("tbody");
tableBody.append(tableBody.html());
}
});
};
$('.fixed').isScrolledTo();
See Example http://jsfiddle.net/leviputna/v4q3a/
Question
Clearly my current example is not correct. My question is how to I detect when a user has scrolled to the bottom of a fixed div with overflow:scroll set?
Using the bottom element is a bit clunky, I think. Instead, why not use the scrollHeight and height to test once the scrollable area has run out.
$.fn.isScrolledTo = function () {
var element = this,
tableBody = this.find("tbody");
element.scroll(function(){
if( element.scrollTop() >= element[0].scrollHeight-element.height()){
tableBody.append(tableBody.html());
}
});
};
$('.fixed').isScrolledTo();
EDIT (12/30/14):
A DRYer version of the plugin might be much more re-usable:
$.fn.whenScrolledToBottom = function (cback_fxn) {
this.on('scroll',this,function(){
if( ev.data.scrollTop() >= ev.data[0].scrollHeight - ev.data.height()){
return cback_fxn.apply(ev.data, arguments)
}
});
};
Plugin Usage:
var $fixed = $('.fixed'),
$tableBody = $fixed.find("tbody");
$fixed.whenScrolledToBottom(function(){
// Load more data..
$tableBody.append($tableBody.html());
});
I have modified your code to handle the scroll event with a timer threshold:
$.fn.isScrolledTo = function () {
var element = $(this);
var bottom = element.find('.bottom');
$(element).scroll(function(){
if (this.timer) clearTimeout(this.timer);
this.timer=setTimeout(function(){
if( element.scrollTop() >= bottom.position().top){
var tableBody = element.find("tbody");
tableBody.append(tableBody.html());
}
},300);
});
};
$('.fixed').isScrolledTo();
The issue you are having is that as you scroll, new scroll event is being generated. Your code might have other issues, but this is a start.

Get divs within viewport inside a wrapper div

Is there a way to get elements which is:
Inside a div with overflow: scroll
Is in viewport
Just like the following picture, where active div (5,6,7,8,9) is orange, and the others is green (1-4 and >10) :
I just want the mousewheel event to add "active" class to div 5,6,7,8,9 (currently in viewport). View my JSFiddle
$('.wrapper').bind('mousewheel', function (e) {
//addClass 'active' here
});
You could do something like this. I would have re-factored it, but only to show the concept.
Firstly I would attach this to scroll event and not mousewheel. There are those among us that likes to use keyboard for scrolling, and you also have the case of dragging the scrollbar. ;) You also have the case of touch devices.
Note that with this I have set overflow:auto; on wrapper, thus no bottom scroll-bar.
With bottom scrollbar you would either have to live with it becoming tagged as in-view a tad to early, or tumble into the world of doing a cross-browser calculating of IE's clientHeight. But the code should hopefully be OK as a starter.
»»Fiddle««
function isView(wrp, elm)
{
var wrpH = $(wrp).height(),
elmH = $(elm).height(),
elmT = $(elm).offset().top;
return elmT >= 0 &&
elmT + elmH < wrpH;
}
$('.wrapper').bind('scroll', function (e) {
$('div.box').each(function(i, e) {
if (isView(".wrapper", this)) {
$(this).addClass('active');
} else {
$(this).removeClass('active');
}
});
});
Note that you should likely refactor in such a way that .wrapper height is only retrieved once per invocation, or if it is static, at page load etc.
Update; a modified version of isView(). Taking position of container into account. This time looking at dolphins in the pool.
»»Fiddle««
function isView(pool, dolphin) {
var poolT = pool.offset().top,
poolH = pool.height(),
dolpH = dolphin.height(),
dolpT = dolphin.offset().top - poolT;
return dolpT >= 0 && dolpT + dolpH <= poolH;
}

How to listen for layout changes on a specific HTML element?

What are some techniques for listening for layout changes in modern browsers? window.resize won't work because it only fires when the entire window is resized, not when content changes cause reflow.
Specifically, I'd like to know when:
An element's available width changes.
The total height consumed by the in-flow children of an element changes.
There are no native events to hook into for this. You need to set a timer and poll this element's dimensions in your own code.
Here's the basic version. It polls every 100ms. I'm not sure how you want to check the children's height. This assumes they'll just make their wrapper taller.
var origHeight = 0;
var origWidth = 0;
var timer1;
function testSize() {
var $target = $('#target')
if(origHeight==0) {
origWidth = $target.outerWidth();
origHeight = $target.outerHeight();
}
else {
if(origWidth != $target.outerWidth() || origHeight = $target.outerHeight()) {
alert("change");
}
origWidth = $target.outerWidth();
origHeight = $target.outerHeight();
timer1= window.setTimeout(function(){ testSize() }),100)
}
}
New browsers now have ResizeObserver, which fires when the dimensions of an element's content box or border box are changed.
const observer = new ResizeObserver(entries => {
const entry = entries[0];
console.log('contentRect', entry.contentRect);
// do other work here…
});
observer.observe(element);
From a similar question How to know when an DOM element moves or is resized, there is a jQuery plugin from Ben Alman that does just this. This plugin uses the same polling approach outlined in Diodeus's answer.
Example from the plugin page:
// Well, try this on for size!
$("#unicorns").resize(function(e){
// do something when #unicorns element resizes
});

Is it possible to click through a movable div?

I am working on some jQuery/JavaScript that makes it possible to drag a div around and simultaneously be able to manipulate other divs (specifically images) on the page. The movable div is basically a transparent rectangle that is meant to simulate a lens. The problem I am having is that I cannot figure out how to pass clicks through to the images below the movable div. I have read up on the pointer-events CSS property and tried setting that to none for the movable div, but that makes the movable div no longer movable. Is there a way for me to pass clicks through this movable div while keeping it movable?
EDIT: To all those asking for my current code, here is the JavaScript that I have so far:
<script>
$(document).ready(function(){
$('img').click(function(e) {
$(document).unbind('keypress');
$(document).keypress(function(event) {
if ( event.which == 115) {
$(e.target).css('width', '+=25').css('height', '+=25');
};
if ( event.which == 97) {
$(e.target).css('width', '-=25').css('height', '-=25');
};
});
});
//code to drag the lens around with the mouse
$("#draggableLens").mousemove(function(e){
var lensPositionX = e.pageX - 75;
var lensPositionY = e.pageY - 75;
$('.lens').css({top: lensPositionY, left: lensPositionX});
});
});
</script>
I created a demo that is proof of concept using document.elementFromPoint to locate the nearest image the moveable element is over. I used jQueryUI draggable to simplify event handling.
The trick with using document.elementFromPoint is you must hide the element you are dragging just long enough to look for other elements, or the draggging element is itself the closest element.
Adding an active class to the closest element allows clicking on the viewer to access the active element
Demo code uses LI tags instead of IMG
var $images = $('#list li');
timer = false;
$('#viewer').draggable({
drag: function(event, ui) {
if (!timer) {
timer = true;
var $self = $(this);
/* use a timeout to throttle checking for the closest*/
setTimeout(function() {
/* must hide the viewer so it isn't returned as "elementFromPoint"*/
$self.hide()
var el = $(document.elementFromPoint(event.pageX, event.pageY));
$('.active').removeClass('active');
if ($el.is('li')) {
$el.addClass('active')
}
$self.show()
timer = false;
}, 100);
}
}
}).click(function() {
if ($('.active').length) {
msg = 'Clicked on: ' + $('.active').text();
} else {
msg = 'Click - No active image';
}
$('#log').html(msg + '<br>');
})
DEMO: http://jsfiddle.net/nfjjV/4/
document.elementFromPoint is not be supported in older browsers. You could also use jQuery position or offset methods to compare coordinates of elements with the current position of the viewer for full browser compatibility

document.ontouchmove and scrolling on iOS 5

iOS 5 has brought a number of nice things to JavaScript/Web Apps. One of them is improved scrolling. If you add
-webkit-overflow-scroll:touch;
to the style of a textarea element, scrolling will work nicely with one finger.
But there's a problem. To prevent the entire screen from scrolling, it is recommended that web apps add this line of code:
document.ontouchmove = function(e) {e.preventDefault()};
This, however, disables the new scrolling.
Does anyone have a nice way to allow the new scrolling within a textarea, but not allow the whole form to scroll?
Update Per Alvaro's comment, this solution may no longer work as of iOS 11.3.
You should be able to allow scrolling by selecting whether or not preventDefault is called. E.g.,
document.ontouchmove = function(e) {
var target = e.currentTarget;
while(target) {
if(checkIfElementShouldScroll(target))
return;
target = target.parentNode;
}
e.preventDefault();
};
Alternatively, this may work by preventing the event from reaching the document level.
elementYouWantToScroll.ontouchmove = function(e) {
e.stopPropagation();
};
Edit For anyone reading later, the alternate answer does work and is way easier.
The only issue with Brian Nickel's answer is that (as user1012566 mentioned) stopPropagation doesn't prevent bubbling when you hit your scrollable's boundaries. You can prevent this with the following:
elem.addEventListener('touchstart', function(event){
this.allowUp = (this.scrollTop > 0);
this.allowDown = (this.scrollTop < this.scrollHeight - this.clientHeight);
this.prevTop = null;
this.prevBot = null;
this.lastY = event.pageY;
});
elem.addEventListener('touchmove', function(event){
var up = (event.pageY > this.lastY),
down = !up;
this.lastY = event.pageY;
if ((up && this.allowUp) || (down && this.allowDown))
event.stopPropagation();
else
event.preventDefault();
});
For anyone trying to acheive this with PhoneGap, you can disable the elastic scrolling in the cordova.plist, set the value for UIWebViewBounce to NO. I hope that helps anyone spending ages on this (like i was).
ScrollFix seems to be perfect solution. I tested it and it works like a charm!
https://github.com/joelambert/ScrollFix
/**
* ScrollFix v0.1
* http://www.joelambert.co.uk
*
* Copyright 2011, Joe Lambert.
* Free to use under the MIT license.
* http://www.opensource.org/licenses/mit-license.php
*/
var ScrollFix = function(elem) {
// Variables to track inputs
var startY, startTopScroll;
elem = elem || document.querySelector(elem);
// If there is no element, then do nothing
if(!elem)
return;
// Handle the start of interactions
elem.addEventListener('touchstart', function(event){
startY = event.touches[0].pageY;
startTopScroll = elem.scrollTop;
if(startTopScroll <= 0)
elem.scrollTop = 1;
if(startTopScroll + elem.offsetHeight >= elem.scrollHeight)
elem.scrollTop = elem.scrollHeight - elem.offsetHeight - 1;
}, false);
};
It was frustrating to discover a known problem with stopPropagation and native div scrolling. It does not seem to prevent the onTouchMove from bubbling up, so that when scrolling beyond the bounds of the div (upwards at the top or downwards at the bottom), the entire page will bounce.
More discussion here and here.

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