How do I synchronize the scroll position of two divs?
I know this is an old thread, but maybe this will help someone. In case if you need to synchronize scrolling in double direction, it's not good enough to just handle both containers' scrolling events and set the scroll value, because then scrolling events are getting into cycle and the scrolling is not smooth (try to scroll vertically by a mouse wheel an example given by Hightom).
Here is an example of how you can check if you are already synchronizing the scroll:
var isSyncingLeftScroll = false;
var isSyncingRightScroll = false;
var leftDiv = document.getElementById('left');
var rightDiv = document.getElementById('right');
leftDiv.onscroll = function() {
if (!isSyncingLeftScroll) {
isSyncingRightScroll = true;
rightDiv.scrollTop = this.scrollTop;
}
isSyncingLeftScroll = false;
}
rightDiv.onscroll = function() {
if (!isSyncingRightScroll) {
isSyncingLeftScroll = true;
leftDiv.scrollTop = this.scrollTop;
}
isSyncingRightScroll = false;
}.container {
width: 200px;
height: 500px;
overflow-y: auto;
}
.leftContainer {
float: left;
}
.rightContainer {
float: right;
}<div id="left" class="container leftContainer">
Sed ut perspiciatis, unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam eaque ipsa, quae ab illo inventore veritatis et quasi architecto beatae vitae dicta sunt, explicabo. Nemo enim ipsam voluptatem, quia voluptas sit, aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos, qui ratione voluptatem sequi nesciunt, neque porro quisquam est, qui dolorem ipsum, quia dolor sit, amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt, ut labore et dolore magnam aliquam quaerat voluptatem. Ut enim ad minima veniam, quis nostrum exercitationem ullam corporis suscipit laboriosam, nisi ut aliquid ex ea commodi consequatur? Quis autem vel eum iure reprehenderit, qui in ea voluptate velit esse, quam nihil molestiae consequatur, vel illum, qui dolorem eum fugiat, quo voluptas nulla pariatur? At vero eos et accusamus et iusto odio dignissimos ducimus, qui blanditiis praesentium voluptatum deleniti atque corrupti, quos dolores et quas molestias excepturi sint, obcaecati cupiditate non provident, similique sunt in culpa, qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio, cumque nihil impedit, quo minus id, quod maxime placeat, facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet, ut et voluptates repudiandae sint et molestiae non recusandae. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat.
</div>
<div id="right" class="container rightContainer">
Sed ut perspiciatis, unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam eaque ipsa, quae ab illo inventore veritatis et quasi architecto beatae vitae dicta sunt, explicabo. Nemo enim ipsam voluptatem, quia voluptas sit, aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos, qui ratione voluptatem sequi nesciunt, neque porro quisquam est, qui dolorem ipsum, quia dolor sit, amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt, ut labore et dolore magnam aliquam quaerat voluptatem. Ut enim ad minima veniam, quis nostrum exercitationem ullam corporis suscipit laboriosam, nisi ut aliquid ex ea commodi consequatur? Quis autem vel eum iure reprehenderit, qui in ea voluptate velit esse, quam nihil molestiae consequatur, vel illum, qui dolorem eum fugiat, quo voluptas nulla pariatur? At vero eos et accusamus et iusto odio dignissimos ducimus, qui blanditiis praesentium voluptatum deleniti atque corrupti, quos dolores et quas molestias excepturi sint, obcaecati cupiditate non provident, similique sunt in culpa, qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio, cumque nihil impedit, quo minus id, quod maxime placeat, facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Temporibus autem quibusdam et aut officiis debitis aut rerum necessitatibus saepe eveniet, ut et voluptates repudiandae sint et molestiae non recusandae. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat.
</div>Here is the fiddle.
$('#bottom').on('scroll', function () {
$('#top').scrollTop($(this).scrollTop());
});
Here we are using .scrollTop() for all it's worth, getting the scrollTop value from the element with scroll-bars, and setting the scrollTop for the other element to sync their scroll positions: http://api.jquery.com/scrollTop
This assumes that your bottom element has an ID of bottom and your top element has an ID of top.
You can hide the scroll-bars for the top element using CSS:
#top {
overflow : hidden;
}
Here is a demo: http://jsfiddle.net/sgcer/1884/
I suppose I've never really had a reason to do this, but it looks pretty cool in action.
I've been looking for a double direction solution and thanks to you all, your contibutions helped me doing this :
$('#cells').on('scroll', function () {
$('#hours').scrollTop($(this).scrollTop());
$('#days').scrollLeft($(this).scrollLeft());});
See on JSFiddle : https://jsfiddle.net/sgcer/1274/
Hope it's help someone someday :-)
Alright, so I evaluated all of the options presented here, and they all had limitations of one form or another:
- The accepted answer suffers from known issues using the mouse scroll wheel.
- The next highest upvote does not have scroll wheel issues, but only works for two known elements. If you need more elements, it's not scalable.
- The only solution that showed promise was Lacho's, but there were known element references in the code that were not included in the snippet. On the plus side, it had the structure needed for performance, and it's in TypeScript.
I leveraged that to create a reusable version that can work with an unlimited number of elements, and it doesn't require JQuery.
function scrollSync(selector) {
let active = null;
document.querySelectorAll(selector).forEach(function(element) {
element.addEventListener("mouseenter", function(e) {
active = e.target;
});
element.addEventListener("scroll", function(e) {
if (e.target !== active) return;
document.querySelectorAll(selector).forEach(function(target) {
if (active === target) return;
target.scrollTop = active.scrollTop;
target.scrollLeft = active.scrollLeft;
});
});
});
}
//RWM: Call the function on the elements you need synced.
scrollSync(".scrollSync");
You can check out the JSFiddle for this here: http://jsfiddle.net/gLa2ndur/3. You can see it uses both horizontal and vertical scrolling examples.
The only known limitation is that it might not work on divs of different sizes. I'm sure someone can work on incorporating Andrew's work into this if your use-case finds that necessary (mine does not).
I hope this is helpful to someone!