Is there any way to control scroll bar using JavaScript? - javascript

In my below code a function to scroll DIV for every set of intervals where when I try to scroll up due to interval refresh scroll bar again coming down.
My code:
var int = self.setInterval("f2()", 1000);
function f2() {
var objDiv = document.getElementById("messages2");
objDiv.scrollTop = objDiv.scrollHeight;
}
Now, by using onscroll property for DIV is there anyway to stop scrolling down when holding scroll bar with mouse?
Something like
var int = self.setInterval("f2()", 1000);
function f2() {
var objDiv = document.getElementById("messages2");
// if(objDiv.onscroll) i.e. when the particular DIV's scroll bar is on hold by cursor.
{
return false;
}
else
{
objDiv.scrollTop = objDiv.scrollHeight;
}
}
If the above kind of function can be implemented anybody please correct its syntax. I am a newbie to JavaScript.
Thanks in advance..!

I’m not sure what you are asking here, but window has a scroll event that you can listen to, and so does any other element that has overflow: auto|scroll set using CSS.
You can’t prevent the default scrolling behavior, but you can use the scrollTo() method or the scrollTop property if you want to do something annoying like:
window.onscroll = function() {
window.scrollTo(0,0);
};
Here is a nice compat table of the scroll event: http://www.quirksmode.org/dom/events/scroll.html
scrollTo() docs: https://developer.mozilla.org/en/Window.scrollTo

Related

How to Synchronize Scroll Between two windows

I have a popup window in my site that show additional information about the elements been show in the main screen. I need to syncronize the scrolling between the two windows, in a way that when the user scroll one of the window , the other window is automatticaly scrolled in the same ammount.
I was able to do that using jquery scroll event, and using the scrollTop function to set the scroll position. something like this:
$("#localDiv").scroll(function() {
var scrollPos = $("#localDiv").scrollTop();
$("targetElement").scrollTop( scrollPos );
});
I've simplified the actual code, because I have to do some work to reach the elements in another window, but this is not the question.
The problem is, this code works fine in Chrome and IE, but in FireFox the scrolling gets really slow.
I've created an example here : http://jsfiddle.net/Lv2dw787/4/. The problem seems to ocurr with DIV's in the same page as well. You can note that when the scrolling syncing is disabled, the speed turn back to normal.
Does anyone have a clue on how to fix this on FireFox?
Edit after Dave Chen answer:
The accepted answer solved my problem, but it has a catch. I first tried to do this:
lock = true;
try {
var scrollPos = $("#contentDivA").scrollTop();
$("#contentDivB").scrollTop( scrollPos );
}
finally
{
lock = false;
}
But the $("#contentDivB").scrollTop( scrollPos ); line seems to generate a scroll event on divB only after the current function finishes executing, so the finally part of try..finally was executing before that. So I had to this:
lock = true;
var scrollPos = $("#contentDivA").scrollTop();
$("#contentDivB").scrollTop( scrollPos );
and on DivB scroll event:
if (lock)
lock = false;
else {
(Do the scroll on DivA)
}
The reason is because of two reasons:
Firefox does smoothing on its scrolling
jQuery's scrollTop will trigger events
Let's look at some pseudo-code:
When divA is scrolled -> scroll divB to the same spot
When divB is scrolled -> scroll divA to the same spot
The problem is that when you scroll divA or divB to the same spot, it will also cause the when to happen again.
So for example, when you scroll divA, this is what happens:
scroll divA -> scroll divB to the same spot -> scroll divA to the same spot
This causes divA to stick to the same spot after scrolling a little, and thus what causes the sluggish effect in firefox.
A solution is to ignore scrolling events when you scroll:
$(document).ready(function() {
var ignore = false;
$("#contentDivA").scroll(function() {
var tmpIgnore = ignore;
ignore = false;
if (!tmpIgnore && $("#chkSyncEnabled")[0].checked)
{
var scrollPos = $("#contentDivA").scrollTop();
scrollTop($("#contentDivB"), scrollPos);
}
});
$("#contentDivB").scroll(function() {
var tmpIgnore = ignore;
ignore = false;
if (!tmpIgnore && $("#chkSyncEnabled")[0].checked)
{
console.log("here");
var scrollPos = $("#contentDivB").scrollTop();
scrollTop($("#contentDivA"), scrollPos);
}
});
function scrollTop(el, position) {
ignore = true;
el.scrollTop(position);
}
});
Example

Disable all scrolling on webpage

I would like to know if it is possible to disable all scrolling on a webpage.
I am currently using
html, body { overflow:hidden; }
The issue is that this does not work on iOS devices and if you hold in the mouse wheel and drag it down you can also scroll, so it seems like a very poor solution to the problem
Is there a way to disable all methods of scrolling on all devices and then re-enable it?
I have had this exact same issue, i fixed it with the following;
var disableScroll = false;
var scrollPos = 0;
function stopScroll() {
disableScroll = true;
scrollPos = $(window).scrollTop();
}
function enableScroll() {
disableScroll = false;
}
$(function(){
$(window).bind('scroll', function(){
if(disableScroll) $(window).scrollTop(scrollPos);
});
$(window).bind('touchmove', function(){
$(window).trigger('scroll');
});
});
the touch move is bound to the window as the window scroll event is not fired until touch move is completed, so this allows a much smoother experience on iOS!
This isn't a perfect solution as you can 'throw' the page, but it will return to desired position when the throw has complete (as the window scroll event will then be fired). This is because iOS browsers strip out a lot of events for performance. also setTimeout and setInterval functions do not fire whilst the page is being thrown, having a loop isn't an option either!
see here http://jsfiddle.net/8T26k/

Div overflow custom position

I'm trying to scroll to a desired position when the page loads. The scroll bar is inside a div. Here is the code:
function scroll()
{
document.getElementById('content').scrollTo(500,500);
}
but its not working, any sugestions as my JavaScript is pretty bad???
Converting Ian's comment to an answer:
scrollTo only applies to the window, not individual elements. These have scrollTop and scrollLeft properties that you can change:
function scroll(elem,x,y) {
elem.scrollLeft = x;
elem.scrollTop = y;
}
// to call:
scroll(document.getElementById('content'),500,500);

Getting bottom scroll.y when scrolling to the bottom

I'm using a nicescroll a plugin that I use to create scrollbars on divs.
$('#postscroller').niceScroll();
var nice = $("#postscroller").getNiceScroll()[0];
$('#postscroller').bind("scroll",function()
{
if(nice.scrollvaluemax==nice.scroll.y)
{
alert('bottom');
}
alert(nice.scroll.y);
});
First I activate the div to be scrolled.
Then I save the nicescroll instance to the nice variable.
When I test the scroll event to see wether the scroll.y is being fired when I scroll to the bottom I get some numbers but not 134 which is nice.scrollvaluemax in the div I'm testing.
I do get however 134 when I'm at the bottom and I scroll upwards.
Any idea on how can I get 134 when scrolling to the bottom?
Thanks
you get other numbers because you are not at the bottom when you scroll down...
probably related to your current position when the scroll is fired.
post more code.
I fixed it by calling this at the scroll event
var postscrollertimer = (function() {
var timer;
return function() {
clearTimeout(timer);
timer = setTimeout(function()
{
if(postscroller.scrollvaluemax==postscroller.scroll.y)
{
//do stuff
}
}, 1000);
};
})();

Div Overflow Scroll-to-bottom: Is it possible?

If I have a div with overflow:auto so that it is a scrollable div and I load it with information that makes a significant scroll area, is there a way that when I load the information, the div shows the bottom results? Or essentially scrolls to the bottom?
I've seen jQuery solutions but this is for use in an HTA so I cannot use jQuery. Is there a purely javascript way to accomplish this?
var myDiv = document.getElementById('myDiv');
myDiv.scrollTop = myDiv.scrollHeight;
Works in Firefox, Safari, Opera, Chrome and even Internet Explorer, which is more than I can say for the SSE test case I Set up... lol
I will spare you the rant about the obtuse solutions offered by others, and here is an example of code that could be used for an instant messaging type client.
document.body.onload = function()
{
var myDiv = document.getElementById('myDiv');
// Pick your poison below, server sent events, websockets, AJAX, etc.
var messageSource = new EventSource('somepage');
messageSource.onmessage = function(event)
{
// You must add border widths, padding and margins to the right.
var isScrolled = myDiv.scrollTop == myDiv.scrollHeight - myDiv.offsetHeight;
myDiv.innerHTML += event.data;
if(isScrolled)
myDiv.scrollTop = myDiv.scrollHeight;
};
};
The part of that example that is relevant checks to see if the div is already scrolled to the bottom, and if it is, scrolls it to the bottom after adding data to it. If it is not already scrolled to the bottom, the div's scroll position will stay such that the visible content of the div is unaffected by adding the data.
document.getElementById('mydiv').scrollTop = 9999999;
The scrollTop property specifies the scrolling offset in pixels from the top of the region. Setting it to a very large value will force it to the bottom.
How about this?
function scroll_to_max(elm) { // {{{
if(!scroll_to_max_el) {
scroll_to_max_el = elm;
setTimeout(scroll_to_max, 10); // Allow for the element to be updated
} else {
var el = scroll_to_max_el;
var t = el.scrollTop;
el.scrollTop = t+100;
if(el.scrollTop != t) {
setTimeout(scroll_to_max, 10); // Keep scrolling till we hit max value
} else {
scroll_to_max_el = null;
}
}
}
var scroll_to_max_el = null; // Global var!
// }}}
(NOTE: Only tested it in Chrome...)
Late answer but this is much more helpful
$('#mydiv').scrollTop(($('#mydiv').height()*2));
I think you need to set the scrollTop after the element is updated.
setTimeout(function (){
el.scrollTop = 999999999
}, 10)
also, in chrome at least, 99999999999 will scroll to the bottom. but 999999999999 (an extra 9) will scroll to the top. it's probably converted to an int in the C side of webkit.

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