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Animating an element differently to slide in/out of view on scroll up / down

I'm working on a new portfolio for myself, using Bootstrap framework and I want to animate my slider based on the direction that the user is scrolling.
For example I already have an animation to slide the navbar class in. But as the user scrolls down the page I want to hide the navbar this is to give the user more visibility on the screen when browsing content. Then when they attempt to scroll back up the page I want to slide the .navbar class back in again.
Now I can easily get this to work if I target a specific element or pixel height, but that doesn't help me. I know it's achievable as I've seen it on several websites (LinkedIn for example).
So I'm wondering if it's a case of targeting positive or negative values on the y axis or something?

var lastScrollPosition = 0;
window.onscroll = function() {
var newScrollPosition = window.scrollY;
if (newScrollPosition < lastScrollPosition){
//upward - code here
}else{
//downward - code here
}
lastScrollPosition = newScrollPosition;
}

Script to stop fixed div from scrolling under another div?

https://rebecca-milazzo-test.squarespace.com/featured#/btr/
I have the page meta-data set to fixed positioning, but as the users scroll, the div doesn't stop and scrolls under the thumbnails at the bottom of the page. I have researched other scripts, but they all are created to stop the div at a certain pixel height and not another element.
Any help is greatly appreciated.

You're going to want to create a function that checks the windows scroll position to see whether you've scrolled to the thumbnails section. When you've scrolled to the thumbnails section, set the fixed elements position to absolute and set its top to the windows scroll position plus the original top value. For those like myself who thought z-index would suffice, OP doesn't want the element to go either underneath the thumbnails section or above the thumbnails section on scroll.
function checkposition(){
fixedelement = document.querySelector(".project-meta");
stopelement = document.querySelector("#project-thumbs");
stoppoint = stopelement.scrollTop - fixedelement.clientHeight - parseInt(fixedelement.style.top);
if (window.scrollY >= stoppoint){
fixedelement.style.position = "absolute";
fixedelement.style.top = [defaulttophere] + window.scrollY + "px";
} else {
fixedelement.style.position = "fixed";
fixedelement.style.top = [defaulttophere];
}
}
window.addEventListener("scroll", checkposition);
Let me know if this works or not, I threw this together pretty quickly.

Hide only one element in fixed div when scrolling down

I have this big photo which takes 100%x100% of screen size and above it there is fixed slider.
I want to fadeout (hide) this green logo when you scroll down from this big header photo leaving navigation bar without it.
How can I do that?
http://i.stack.imgur.com/BiUfE.jpg here is photo

If you want the logo to scroll with the page, just put it outside of the menu bar in your HTML and use position absolute (JS Fiddle).
If you want it to fade out once it leaves the slider, you can use jQuery, here is an example:
//Some variables, to avoid calculating these values at every scroll
var logo = $('#logo');
var sliderBottom = $('#slider').offset().top + $('#slider').height() - logo.height();
//On every scroll
$(window).scroll(function(){
// if we're past the slider and the logo is still visible
if($(window).scrollTop()>sliderBottom && logo.is(':visible')){
logo.stop().fadeOut(300);
}
// if not
else if($(window).scrollTop()<sliderBottom && logo.is(':hidden')){
logo.stop().fadeIn(300);
}
});
JS Fiddle Demo

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.

Absolute position element left or right depending where it is?

How can I assign absolute left 0px OR absolute right 0px depending on if the absolute positioned div will go outside of its container div.
I guess an easy example of what I mean is: right click in your browser, see it has that menu position to the right of where you click, well not go all the way to the right of the page, instead of going outside of the page, it stays inside of it so it's still visible.
example: (Hover over boxes)
http://jsfiddle.net/ueSNQ/1/

It sounds like you'll need to use script to work the "depending on if the absolute positioned div will go outside of its container div" bit, IE supports css expressions but you're probably after a cross browser solution.
that said it should be a simple matter of something like this
function isOverflow(parent, child){
var left = 0;
var op = child;
while(op && op != parent){
left += op.offsetLeft;
op = op.offsetParent;
}
return ((left + child.offsetWidth) > parent.offsetWidth);
}
function getHoverHandler(parent, child){
return function(){
if(isOverflow(parent, child)){
child.style.marginLeft = 'auto';
child.style.right = '0px';
child.style.left = '';
}
}
}
function attach(o,e,f){
if(o.addEventListener){
o.addEventListener(e, f, false);
}else if(o.attachEvent){
o.attachEvent('on'+e,f);
}
}
var yellowElement = document.getElementsByTagName('UL')[0];
var list= document.getElementsByTagName('LI');
for(var i = 0; i < list.length; i++){
var element = list[i];
var tip = element.getElementsByTagName('DIV')[0];
attach(element, 'mouseover', getHoverHandler(yellowElement,tip));
}

Well Friend,
Try the following steps
1. You have a container div and on right clicking on it you will need to display a div for example say div with list of menus.
2. Have the left position of the container div in a variable **contLeft** and width of the container in another variable **contWidth**
3. Assign the oncontextmenu event handler on the container div.
4. In the event handler function take the mouse x postion in a variable **mosX** and mouse y position in a variable **mosY** and you have to fix the top position of the div to be displayed as mosY and the left as mosX.
5. In order to maintain the div within the container you have to calculate the container's screen occupation as **totPos = (contLeft + contWidth)**
6. Calculate the screen occupation of the menu div as **posMenu = (mosX + width of the div)**
7. If the totPos greater than or equal to posMenu display the menu in the same top and left postion using the values of mosY and mosX
8. Else place the menu in position top = mosY and left = (mosX - width of menu div)
Hope this would solve your problem.

Well first of all if the container div has a position set than position: absolute, right: 0px or left: 0px will be positioned relatively to the container's position. Else it will be positioned to the first parentNode going up the tree from the desired div which has a position, if none is found it will be relative to the body. So you can search the first parent or grandparent container that has a position set. The question is hard to understand so if you would like to share some examples we would be glad to help.
EDIT:
In the example you posted it is exactley like in my comment, calculate the offsethWidth of the parent and the offsetWidth + left to not be overflowing if it is decrease the left or just remove left and set the right positioning. For the same effect on width and height you have to make some cases for the corners.