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Position element in centre of visible viewport window with overflow-y:scroll

I've rather roughly built this website which uses an effect similar to the iOS Safari tab view to look at various pages of a virtual book. Everything is working fine apart from the fact that I can't centre each page in the visible viewport. For example if you scroll down to the final 'page' and click on it, it jumps to the top of the document, instead of staying in the centre of the visible viewport.
I think this is to do with the fact that the scrollable div uses overflow-y:scroll, but I just can't figure out for the life of me how to fix the problem.
Any help would be greatly appreciated!!
Here's my jQuery:
jQuery(document.body).on('click', '.page', function() { //Change to touchstart
// Generate number between 1 + 2
var randomClass = 3;
var randomNumber = Math.round(Math.random() * (randomClass - 1)) + 1;
// Initialise & Random Number
jQuery(this).addClass("activated").addClass('scaled-' + randomNumber);
// Exiting - Reset All
jQuery(document.body).on('click', '.activated', function() { //Change to Touchstart
jQuery(this).removeClass("activated scaled-1 scaled-2 scaled-3");
});
});
And here is a jsfiddle with all my code in it so you can get a better idea of what I'm trying to achieve.
https://jsfiddle.net/ontu1ngq/
Thanks!

You need to get the amount that #wrapper has been scrolled, so that you can use that to set the top of the .page accordingly. Then, when you remove the .activated class, you will just need to remove the inline top style.
jQuery(document.body).on('click', '.page', function() {
var randomClass = 3;
var randomNumber = Math.round(Math.random() * (randomClass - 1)) + 1;
jQuery(this).addClass("activated").addClass('scaled-' + randomNumber);
var wrapper_scrollTop = $("#wrapper").scrollTop(); //gets amount scrolled
var half_wrapper = $("#wrapper").height()*(0.5); //50% of wrapper height
jQuery(this).css("top",half_wrapper+wrapper_scrollTop);
jQuery(document.body).on('click', '.activated', function() {
jQuery(this).removeClass("activated scaled-1 scaled-2 scaled-3");
jQuery(this).css("top","") //returns top to original value specified in css
});
});
Check out this working fiddle: https://jsfiddle.net/tardhepc/1/

Parallax background image for top-bottom and not right-left

I wrote a script that changes the BG position as you scroll down, its works good for left and right positions but i cant seem to reach the syntax that will allow me to parallax the background-position top or bottom - instead of right and left.
here is my code:
function parallax(){
var scrolled = $(window).scrollTop();
$('section.intro .custombg').css('background-position',(scrolled * -0.2) + 'px');}
$(window).scroll(function(e){
parallax();
});
}

The css attribute background-position has two values, #horizontal #vertical.
See: http://www.w3.org/wiki/CSS/Properties/background-position
Consider something like:
function parallax(){
var scrolledTop = $(window).scrollTop();
var scrolledLeft = $(window).scrollLeft();
$('section.intro .custombg').css('background-position',(scrolledLeft * -0.2) + 'px ' + (scrolledTop * -0.2) + 'px');}
$(window).scroll(function(e){
parallax();
});
}
Also, this seems like it will add the scroll event every time the parallax method is called. To correct this, you could try:
function parallax(top, left) {
$('section.intro .custombg').css('background-position',(left * -0.2) + 'px ' + (top * -0.2) + 'px');}
} // end function
$(document).ready(function() {
$(window).scroll(function(e) {
parallax($(window).scrollTop(), $(window).scrollLeft()); // call the method
});
});

This is all wrong, you are setting up an event handler each time you use $(window).scroll(). You only need to do that once. Try this.
var scrolledTop,
scrolledLeft,
background_position,
$custom_bg;
function parallax(){
scrolledTop = window.scrollY,
scrolledLeft = window.scrollX,
background_position = (scrolledLeft * -0.2) + 'px ' + (scrolledTop * -0.2) + 'px');
console.log('background_position', background_position);
$custom_bg.css('background-position', background_position);
}
$(function() {
$custom_bg = $('section.intro .custombg');
$(window).on('scroll', parallax);
});

try
function parallax(){
var scrolled = $(window).scrollTop();
$('section.intro .custombg').css('background-position','center ' + (scrolled * -0.2) + 'px');}
$(window).scroll(function(e){
parallax();
});
}

If you're looking to do more with parallax and change other properties as, I'd highly recommend the Skrollr library (https://github.com/Prinzhorn/skrollr).
You can vary almost any CSS property as you scroll, giving you more options than just background position or something else. It might be more than you're looking for, but it's pretty lightweight and has mobile support, too (which you could have trouble accounting for without a well-developed library). Hope it helps!
For example, if you wanted to shift the background-position of a background image, you could simply do the following:
initialize skrollr (in this case without options, but there are parameters you can set)
<script type="text/javascript">
var s = skrollr.init();
</script>
Then, you're able to use simple data-tags to tell Skrollr which elements you want to make fancy and which you don't. In your case, you could do something vaguely like the following:
(whatever element you want to use parallax on)
<div data-0="background-color:rgb(0,0,255);transform[bounce]:rotate(0deg);" data-500="background-color:rgb(255,0,0);transform[bounce]:rotate(360deg);">
WOOOT
</div>
However, you'd swap background-color out for background-position
<div data-0="background-position: 0px 0px" data-700="background-position: 0px 100px"> </div>
or
<div data-0="background-position: top center" data-700="background-position: bottom center"> </div>
You can use any of the accepted CSS background-position keywords.
Useful:
https://github.com/Prinzhorn/skrollr

Get the position of the scrollbar using javascript

So I am trying to show a tooltip like box as I scroll my webpage and I would like it to follow the scrollbar along the right side of the page.
I looked around and found something to attempt to accomplish that as shown below:
function returnPercentHeight(){
var a = document.getElementById('rightPanel').scrollTop;
var b = document.getElementById('rightPanel').scrollHeight - document.getElementById('rightPanel').clientHeight;
return ((a/b) * 100);
}
I then append a % to the end and set the top margin of the tooltip to that returned value. This works pretty well (sort of) I have to adjust the return((a/b) * x) part (x) to make it follow the scrollbar based on the size of the browser window. Is there a better way to accomplish what I am trying to do? (NOTE: I can only use javascript, no JQuery please.)
EDIT:
Only the div given an ID of 'RightPanel' is scrolling, I am not using the scrollbar on the browser, but a scrollbar on an inner div.

There are three ways to do so:
First:
is to use the fixed position as following;
Position: Fixed;
Second:
With jQuery;
$(function(){
$(window).on('scroll', function() {
var scrollPOS = $(document).scrollTop();
$('.scroll').css({
top: scrollPOS
});
}).scroll();
});
Third:
Same as the previous, only animated;
$(window).on('scroll', function() {
$("#div").stop().animate({
"marginTop": ($(window).scrollTop()) + "px",
"marginLeft":($(window).scrollLeft()) + "px"}, "slow" );
});

Although IE doesn't support, this is the coolest I've seen:
// get
var x = window.scrollX,
y = window.scrollY;
// set
window.scrollTo(1, 2);

jQuery.ScrollTo - how to make bg to scroll slower than the rest?

i'm new to coding , and to this site, i hope you'll help me! so i'm making horizontal website, i want to add scrolling background, that scrolls with other elements clicked, but slower
like for example http://hotdot.pro/en/ . How do i do that, where do i put code lines?
or maybe i could use better plugin?
Thanks for any help!
!!i'm putting script code here just because website says that my post is not informative enough. sorry
<script>
$(document).ready(function() {
$('a.panel').click(function () {
$('a.panel').removeClass('selected');
$(this).addClass('selected');
current = $(this);
$('#wrapper').scrollTo($(this).attr('href'), 800);
return false;
});
$(window).resize(function () {
resizePanel();
});
});
function resizePanel() {
width = $(window).width();
height = $(window).height();
mask_width = width * $('.item').length;
$('#debug').html(width + ' ' + height + ' ' + mask_width);
$('#wrapper, .item').css({width: width, height: height});
$('#mask').css({width: mask_width, height: height});
$('#wrapper').scrollTo($('a.selected').attr('href'), 0);
}
</script>
or
where?

jQuery Parallax Plugin is probably what you are looking for.
See demo here: http://ianlunn.co.uk/plugins/jquery-parallax/
Source code and documentation here: https://github.com/IanLunn/jQuery-Parallax
"or maybe i could use better plugin" - rule of thumb is: whenever it is possible to use already written code (and not to write your own), you should do so. Except the cases, when writing a code is an academic exercise.

Javascript: How to capture the height of the content of a website?

I am trying to find the correct Javascript code to capture the height of all the content on a webpage.
I have looked at document.height, window.screen.height, document.body.offsetHeight, bodyScroll, clientArea.style.height, bodyHeight, and document.documentElement.clientHeight.
I am using FireBug to test these values but all (except for the window.screen.height) seem to change as I resize my window, so they are not actual reporting the actual height of the content.
Now, the window.screen.height never changes, even if I change to different pages with different sizes.
How can I determine the total height of the content? Basically I need to know what the scroll bar knows. Th scrollbar knows how much to scroll per page and how much to scroll to reach the end of the content.
Any help would be greatly appreciated.

Try this:
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.5.1/jquery.min.js" ></script>
<script type="text/javascript">
$(document).ready(function(){
document_height = $(document).height();
document_width = $(document).width();
window_height = $(window).height();
window_width = $(window).width();
alert(document_height + ' x ' + document_width);
alert(window_height + ' x ' + window_width);
});
</script>

Different browers report the size of the window and size of the document in different ways. You can use a library to get around the cross browser problems, like this code in jQuery:
$(document).height();
Without a library, I have used this code to get the dimensions:
var b, h, info;
b = document.body;
h = b.parentNode;
if (window.opera) {
info = { winWidth: b.clientWidth, winHeight: b.clientHeight, pageWidth: h.clientWidth, pageHeight: h.clientHeight };
} else {
info = { winWidth: h.clientWidth, winHeight: h.clientHeight, pageWidth: b.clientWidth, pageHeight: b.clientHeight };
}

var height = Math.max(document.body.scrollHeight, document.documentElement.scrollHeight);