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jquery: how to scroll a div by n pixels

Using jQuery, how do you scroll a div by N more pixels?
So far I tried
$("div.foo").scrollTop(75); //scroll down by 75 pixels

From the jQuery docs for scrollTop:
Description: Get the current vertical position of the scroll bar for
the first element in the set of matched elements or set the vertical
position of the scroll bar for every matched element.
The version of the function you are calling sets the vertical position of the scroll bar from the top of the element, not from the current position. So in order to scroll down from the current position you first have to retrieve your current position. There are a few ways to do that, but you could do something like:
var $foo = $("div.foo");
$foo.scrollTop($foo.scrollTop() + 75); // scroll 75px down from current

If you are looking for Vanilla JavaScript solution like I was, here it is.
const selectedElement = document.querySelector('div.foo');
selectedElement.scrollTop = 75;
querySelector documentation,
scrollTop documentation

the following code may help and you may see this link .
and you can pixel value from window atrributes.Thank you.
var d = $('#div1');
d.scrollTop(d.prop("scrollHeight"));

Using javascript to find the page number of the current view page in an iboooks epub

I am building a lightbox style div element for an ibooks epub. I want the div to be displayed on the current page being viewed at the time. If the image is on page two of the ebook, I want the lightbox to showup on page two. I have the div width and height set to fill the screen.
document.getElementById("LightBoxDiv").style.width=window.innerWidth+"px";
document.getElementById("LightBoxDiv").style.height=window.innerHeight+"px";
I can manualy set a fixed top value of the div if I know which page number an image is on. My device has a 460px height on the window. So for an image on page two, the top should then be 460 which is the beginning of the 2nd page.
document.getElementById("LightBoxDiv").style.top="460px";
However, as ebooks are dynamic in that the user can change the size of the text larger or smaller, the page upon which something might fall changes. I need a way to set the top dynamically based upon the current page. If I know the current page number being viewed, I can set the div top to
var lighboxHeight = (pagenumber-1)*window.innerHeight;
I tried using the window.pageYOffset to calculate the current page, but this always gives a 0 value as the page does not scroll in an ebook. Unfortunately, I can find no documentation or any reference describing how to use javascript to access the page numbers. Does anyone have any idea how to access or find the current page number in an ibooks epub using javascript?
Thanks,--christopher

I believe I found the solution. This question/answer helped a lot.
//window height
var winHeight = window.innerHeight;
//top of object to be placed in the lightbox
//can be any object
var curOjbTop = document.getElementById(svgId).getBoundingClientRect().top;
//body y value
var bodyTop = document.body.getBoundingClientRect().top;
//amount the object is shifted vertically downward from the top of the body element
var offset = curObjTop - bodyTop;
//page number of the object
//this is actually 1 less than the true page number
//it basically starts the page count at 0, but for actual page number add 1
var curPage = Math.floor(offset/winHeight);
//this sets the top edge of the lightbox at y=0 on the page the item is on
var lightboxTop = curPage*winHeight;
document.getElementById("LightBoxDiv").style.top=lightboxTop;
My lightbox div covers the entire viewing area, but if you wanted a smaller one that was centered, you would need to add an additional half of the window height and then set the top margin to be half the negative amount of the height you wanted.
For example if the light box was 200 x 200, then your lightboxtop would be
var lightboxTop = (curpage*winHeight)+(winHeight*.5);
var topMargin = "-100px";
It may need to be tweeked some, but overall it should work to determine a page number.

How do I move the background image of a DIV based on the scrollbar movement?

I have been looking into parallax effects for vertical scrolling on my web page, and after some research, I'm not sure that what I want to do is technically a parallax effect.
From what I've seen, most parallax effects assume you want to be able to scroll indefinitely with many background images rolling by, or with huge images that repeat.
What I want to do is have the background of two DIVs be filled with a background image as the scroll bar reaches the bottom of the page. Note that I do not want the background images to stretch. I'm assuming to get the effect I want that these images would have a vertical height bigger than most people's viewport, and then their vertical position would change. When the user's scrollbar is at the top, a certain amount of the background is visible, and then it moves vertically to fill the background space as the user scrolls down.
Please see the image below for a visual explanation of the effect I hope to acheive:
The height of the veiwport will vary depending on the length of content inside the inner DIV.
My trouble is that if what I am trying to do is not exactly a parallax effect, then I don't know what else to call it, and my attempts to search by describing it keep landing me back at pages offering tutorials on parallax effects. So I've been stumped by a lack of terminology.
If someone could direct me to how I can control the vertical position of the background depending on the scrollbar position, that would be much appreciated. If this can be done with just CSS that would be great, but I'm assuming some Javascript would be required. A jQuery solution would also work for me.
Update:
After searching using the terms provided in comments, I've got the background image in the outer DIV to almost do what I want with the following code:
$(window).scroll(function () {
var yPos = $("#outerDiv").height() - ($("#outerDIV").height() * ($(window).scrollTop() / $(window).height()));
document.getElementById('outerDIV').style.backgroundPosition="0px " + yPos + "px";
});
It moves the background image in the right direction relative to the scrolling, but what it lacks is constraining that motion to within the viewport. Getting the right proportions based on the viewport and DIV sizes is proving to be just a little beyond my mathematical abilities.

For your requirement, you have to use a jquery parallax plugin to guide this activity, my best suggest it to use a Superscollorama and play with the elements as your wish...
As far as your question, Try this example,
controller.addTween(
'#examples-background',
(new TimelineLite())
.append([
TweenMax.fromTo($('#parallax-it-left'), 1,
{css:{backgroundPosition:"(0 -54px)"}, immediateRender:true},
{css:{backgroundPosition:"(0 -54px)"}}),
TweenMax.fromTo($('#parallax-it-right'), 1,
{css:{backgroundPosition:"(0 -54px)"}, immediateRender:true},
{css:{backgroundPosition:"(0 54px)"}})
]),
1000 // scroll duration of tween
);
You serial vice change as far as your wish...
Try practice this plugin, hope that works for you...
http://johnpolacek.github.io/superscrollorama/
Thanks...

Turns out what I want to acheive is possible with no special plugins, just some carefully thought out math. I did use a little jQuery syntax, but I don't think it's strictly necessary.
The code below has copious notes, so hopefully it's largely explanatory. In summary, you just need to find the position of the background image when the scroll would be at the top, and the position it would be if the scroll bar was at the bottom, and then you can use the percentage of the scrollbar's movement to work out where you are between those two points. It's a little tricker than just that, of course, in that you have to account for the difference between the total height of the scroll bar and where your DIV appears on the page and a few other adjustments, but the details of what I did are below.
What I've done here is just for the "outer DIV" that I described in my question. To get a background to move like the "inner DIV" I described, you'd have to modify the code, presumeably by reversing a few parameters. I haven't done that yet, but it seems like a straightforward task.
Hope others find this code useful. If anyone has suggestions on how it can be made more efficient or better, please let me know.
function moveBG(){
// imageHeight is not the total height of the image,
// it's the vertical amount you want to ensure remains visible no matter what.
var imageHeight = 300;
// Get the maximum amount within the DIV that the BG can move vertically.
var maxYPos = $("#outerDIV").height() - imageHeight;
// Get the amount of vertical distance from the top of the document to
// to the top of the DIV.
var headerHeight = document.getElementById("outerDIV").offsetTop;
// Calculate the BG Y position for when the scrollbar is at the very top.
var bgTopPos = $(window).height() - headerHeight - imageHeight;
// I don't want the image to wander outside of the DIV, so ensure it never
// goes below zero.
if (bgTopPos < 0)
{
bgTopPos = 0;
}
// Calculate the BG Y position when the scrollbar is at the very top.
var bgBottomPos = $(document).height() - $(window).height() - headerHeight;
// To prevent the BG image from getting cut off at the top, make sure
// its position never exceeds the maximum distance from the top of the DIV.
if (bgBottomPos > maxYPos)
{
bgBottomPos = maxYPos;
}
// Subtract the top position from the bottom, and you have the spread
// the BG will travel.
var totalYSpan = bgBottomPos - bgTopPos;
// Get the scrollbar position as a "percentage". Note I simply left it as a
// value between 0 and 1 instead of converting to a "true" percentage between
// 0 and 100, 'cause we don't need that in this situation.
var scrollPercent = ($(window).scrollTop() / ( $(document).height() - $(window).height()));
// The percentage of spread is added to the top position, and voila!
// You have your Y position for the BG image.
var bgYPos = bgTopPos + (Math.round(totalYSpan * scrollPercent));
// Apply it to the DIV.
document.getElementById('outerDIV').style.backgroundPosition="0px " + bgYPos + "px";
}
// Place the BG image correctly when opening the page.
$(document).ready(function() {
moveBG();
});
// Make it update when the scrollbar moves.
$(window).scroll(function () {
moveBG();
});

How to determine if HTML Control is being displayed in page?

I'd like to know how could I get only the displayed controls in the screen in the very moment.
For example:
If I have a scrollbar which precludes the user from seeing everything
below the page, I'd like to make a selector which selects only what the user can see in his screen now. It would also be nice If I could select everything he does not see.
Is that possible? How?
Thanks

You could calculate the offsets (say, as the user scrolls) of what the user can see:
var top = $(window).scrollTop();
var bottom = top + $(window).height();
Then, you can see if an element is within this range.
$('*').each( function() {
var el = $(this);
var offsetTop = el.offset().top;
var inView = offsetTop >= top && offsetTop <= bottom;
el.addClass( inView ? 'in-view' : 'out-of-view' );
} );
Obviously there are some downsides performance wise to doing this. Depending what you want to do with this information you could select only inputs or whatever which might help.

I don't know if there is an easy or elegant solution to this. What you could do is calculate the offset position of all elements and the scroll offset to find out which elements are visible or not. This could become expensive if you have a lot of elements to check, but could work quite nicely otherwise.

How do I easily find the distance between a point on the page and the bottom of the browser window using JavaScript?

A view in my web app has a table which may be extremely long, so I wrapped it in a div with overflow: auto; max-height: 400px; so users can scroll through it while keeping the other controls on the page visible.
I want to use a bit of JavaScript to dynamically adjust the max-height CSS property so the div stretches to the bottom of the browser window. How can I determine this value? jQuery solutions are fine.
The table doesn't start at the top of the page, so I can't just set the height to 100%.

Something like this would work I think:
var topOfDiv = $('#divID').offset().top;
var bottomOfVisibleWindow = $(window).height();
$('#divID').css('max-height', bottomOfVisibleWindow - topOfDiv - 100);

I had a very similar problem, except in my case I had a dynamic pop-up element (a jQuery UI Multiselect widget), to which I wanted to apply a max-height so that it never went below the bottom of the page. Using offset().top on the target element wasn't enough, because that returns the x coordinate relative to the document, and not the vertical scroll-position of the page.
So if the user scrolls down the page, the offset().top won't provide an accurate description of where they are relative to the bottom of the window - you'll need to determine the scroll position of the page.
var scrollPosition = $('body').scrollTop();
var elementOffset = $('#element').offset().top;
var elementDistance = (elementOffset - scrollPosition);
var windowHeight = $(window).height();
$('#element').css({'max-height': windowHeight - elementDistance});

window.innerHeight gives you the visible height of the entire window. I did something almost identical recently so I'm pretty sure that's what you need. :) Let me know, though.
EDIT: You'll still need the Y-value of the overflowed div which you can get by document.getElementById("some_div_id").offsetHeight, seeing that .style.top won't give you a result unless it has been specifically set to a point via CSS. .offsetHeight should give you the correct 'top' value.
Then it's just a matter of setting the size of the table to the window height, minus the 'top' value of the div, minus whatever arbitrary wiggle room you want for other content.

something like max-height: 100%, but not to forget the html and body height 100%.