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Hiding a DIV based on screen height with debouncing

I'm working on a page with a simple side nav that has a fixed position, set top: 30%. What I need to happen is at the bottom of the page I want to fade the menu out so it doesn't overlap the footer, the code below works but I think it is checking on scroll so much it takes to long to calculate when you scroll down fast.
Is there a faster/more lightweight way to calculate when to hide the side-nav? I'm not familiar with debouncing but would it help?
Elements:
.body-container-wrapper - total height of page
.footer-container-wrapper - total height of the footer that we want the nav to be hidden at
.internal-side-nav - the menu position: fixed, top: 30%, right: 0
Example Page: http://hsb1.hubspot.com/profile-page-template
Script:
<script type="text/javascript">
$(document).scroll(function () {
var y = $(this).scrollTop();
if (y < $('.body-container-wrapper').outerHeight() - $('.footer-container- wrapper').outerHeight() - 400 ) {
$('.internal-side-nav').fadeIn();
} else {
$('.internal-side-nav').fadeOut();
}
});
</script>

I hadn't heard of debounce so I had to look it up. It could potentially help, but that would be an extra plugin you'd have to include and maintain and it might not work exactly how you want (I didn't see anything indicating that it does "bunches or time frames", just seemed to be bunches, which means it might fire late on you).
Instead, what you could do is throttle it yourself with a little bit of timing.
var scrollTimeInterval = 200; // how often we allow the action to trigger, in ms.
var lastScrollTime = 0;
var scrollTimeoutId = null;
$(document).scroll(function () {
var now = (new Date()).getTime();
var dScrollTime = now - lastScrollTime;
lastScrollTime = now;
if (dScrollTime < scrollTimeInterval) {
// Set a timeout so we catch the last one.
scrollTimeoutId = setTimeout(function() { $(document).scroll(); }, scrollTimeInterval - dScrollTime);
return; // too soon, so we'll skip
}
// Clear any potentially pending timeout.
clearTimeout(scrollTimeoutId);
var y = $(this).scrollTop();
if (y < $('.body-container-wrapper').outerHeight() - $('.footer-container- wrapper').outerHeight() - 400 ) {
$('.internal-side-nav').fadeIn();
} else {
$('.internal-side-nav').fadeOut();
}
});
With this, the scroll event simply won't do anything if it hasn't been a certain amount of time since it last triggered. To ensure we catch the last scroll event (the last one before they stopped scrolling), I added a timeout which will trigger the scroll event one last time. We also have to make sure to clear that if we handle another scroll event before it fires (so we don't double up on it).
You can control the time interval it allows with the first variable. If 200ms feels a bit sluggish, you can reduce it to 100ms or 50ms and see if that gives a better balance.
Hope that helps.

Dealing with scroll events, in certain circumstances, there's not much you can do.
Solution 1: setTimeout that cancels itself on each iteration
This method is most efficient I believe, but maybe not ideal for you, because there will still be 300ms in which the sidenav would visually overlap the footer before it fades out.
var scrollTimeout = false;
$(document).scroll(function(){
clearTimeout(scrollTimeout);
var _this = this; // for the setTimeout function to know what "this" is
scrollTimeout = setTimeout(function(){
// your original code block goes here
// BUT, replace "this" with "_this"
}, 300);
});
The above essentially only runs your code when the user has not scrolled for at least 300 milliseconds.
Solution 2: Just good old optimization (not too many tricks)
This solution should hide the sidenav immediately, but still runs on every scroll, just does less
var myScrollEvent = (function(){
var $win = $(window);
var $foot = $('.footer-container-wrapper');
var footer_top = $foot.offset().top; // where on the page the footer begins
var $nav = $('.internal-side-nav');
var nav_height = $nav.height(); // maybe use outerHeight(true)?...who knows, only you
var is_hidden = false;
// this is the actual function we want to run on-scroll
return function(){
// jquery, even on fixed elements, still seems to account for scroll position
// when calculating top offset value, below is the coordinate of the bottom of the nav
var nav_bottom = $nav.offset().top + nav_height;
// if the bottom coord of the nav is lower than the top coord of the footer
if(nav_bottom > footer_top && !is_hidden){
is_hidden = true;
// hide it code
}else if(is_hidden){
is_hidden = false;
// show it code
}
};
})();
$(window).scroll(myScrollEvent);
The idea here is to cache some variables and also do the calculation a slightly different way. Your way doesn't seem by any means wrong, but this is just an alternative. Note that with this method, we're assuming the nav height will never change.
You could always combine the two solutions if you'd like as well.
Also, note that I haven't done any browser-2-browser testing, so if there are any flaws, of course let me know.

Javascript issue with if statements

ive wrote a simple script that isnt working as intentioned:
var prevscroll = 0;
$(document).scroll(function(){
var currscroll = $(document).scrollTop();
if(currscroll > prevscroll){
$("header").toggle();
prevscroll = currscroll;
}
if(currscroll < prevscroll){
$("header").toggle();
prevscroll = currscroll;
}
});
When the page is scrolled down, its meant to hide the header and only show it if its scrolled up however whats happening is as i scroll down its flicking on and off. :|
I think I may of just spotted a silly error! ofcourse its going to keep flickering since prev scroll keeps increasing.

You can't use toggle() the way you are because the scroll event is called many, many times so if it's called more than once with the same value for your if statement, then it will flicker on, then off, then on, then off each time you call .toggle(). You need to explicitly hide or show when your condition is met.
I don't quite follow exactly what you're trying to do with prevscroll, but perhaps this is what you want:
var prevscroll = 0;
$(document).scroll(function(){
var currscroll = $(document).scrollTop();
if(currscroll > prevscroll){
$("header").hide();
prevscroll = currscroll;
}
if(currscroll < prevscroll){
$("header").show();
prevscroll = currscroll;
}
});
This will hide the header anytime you are scrolling down further and show the header as soon as you start to scroll up.

Window scroll event causing IE to lag badly, when using mouse wheel

I have a navigation container near the top of the page that should add or remove the classname "stuck" (switching between position:static and position:fixed) when the page scrolls beyond a certain value. Seems to work fine in FF and Chrome, but of course IE (7,8 and 9) is having trouble.
The page lags heavily (essentially unusable) when scrolling using the mousewheel, although if I grab and drag the horiz scrollbar then the page slides smoothly with no lag.
My searching around revealed that it's probably because IE executes way more scroll events than the other browsers, but I can't figure out exactly how to throttle the number of events being fired. You can see in the code block below that I'm also using a 'scroll stop' solution but I really need to also be able to execute a callback WHILE the user is still scrolling when they go beyond a certain point on the page.
I thought the way I was implementing it was pretty and stripped down and basic, but is there a better way to handle this, at least just for IE?
var scrollValue = 0;
var scrollTimer = false;
$(window).bind('scroll', function(){
scrollValue = $(window).scrollTop();
// SET TIMER DELAY FOR SCROLL-STOP
if (scrollTimer) {
clearTimeout(scrollTimer);
}
scrollTimer = setTimeout(scrollStopped, 25);
// STICK/UNSTICK HEADER
if (scrollValue > 320){
if (!$(stickyWrap).hasClass('stuck')){
$(stickyWrap).addClass('stuck')
}
} else {
if ($(stickyWrap).hasClass('stuck')){
$(stickyWrap).removeClass('stuck');
}
}
});

Down with timeout, up with switch
If you made the jQuery a little more simple, and added a switch to only execute anything once before and after the threshold, it should speed things up nicely.
var header = $('.stickyWrap'),
trig = 320,
go = true;
$(window).bind('scroll', function(){
var scrollValue = $(this).scrollTop();
if ((go && scrollValue > trig) || (!go && scrollValue <= trig)) {//before or after
header.toggleClass('stuck');//toggle class
go ? go = false : go = true;//toggle boolean
}
});
Now it will only try to execute anything only once before and once after it crosses the threshold of 320.
Made A Fiddle >

Changing div postion depending on page scroll

I have the following code below that changes a div's position to fixed once an element scrollTop is greater than a number. I am trying to either amend this script or find a different solution so that the div will scroll between a range and STOP scrolling at some point ( so the div doesn't go off the page or overlap with footer elements.
I don't know if the right way is to say that IF scrollTop is greater than 150 then position=fixed, and if it's greater than 600 then position goes back to absolute, or if there's a better way, like distance from the bottom...
AND I use MooTools, not jQuery. I know there are a few jQuery options / plugins that do this. Thanks in advance!
window.onscroll = function()
{
if( window.XMLHttpRequest ) { // IE 6 doesnt implement position fixed nicely...
if (document.documentElement.scrollTop > 150) {
$('tabber').style.position = 'fixed';
$('tabber').style.top = '0';
} else {
$('tabber').style.position = 'absolute';
$('tabber').style.top = 'auto';
}
}
}

the script above is wrong on many levels.
don't use window.onscroll but window.addEvent("scroll", function() {});
cache selectors. using $("tabber") 3 times on each scroll when the element does not change is expensive.
just do var tabber = $("tabber") and reference that.
you don't need to do
$("tabber").style.position = ...
$("tabber").style.top = ...
do:
tabber.setStyles({
position: "fixed",
top: 12123,
right: 24
});
There are mootools plugins for this, eg scrollSpy by David Walsh: http://davidwalsh.name/mootools-scrollspy
it can allow you to set scripted events upon reaching various scrolling destinations or events, look at the examples.
or you could just write it yourself, eg, this took me 15 mins to do:
http://jsfiddle.net/dimitar/u9J2X/ (watch http://jsfiddle.net/dimitar/u9J2X/show/) - it stops being fixed when it reaches to 20 px of the footer. and then goes back to fixed if scrolling up again.

fixed div on bottom of page that stops in given place

I have fixed div on bottom of my page that works well. I wonder if there is some simple way to make it "stop" on some place in page when user srolls down to it. I want it to remain fixed on bottom, until user scrolls down to some defined place on page and than stick it to the page and scroll like the rest of content. Any suggestions?

I tried setting something up on jsfiddle. While I was writing it up, I see that others have posted their alternatives. In case mine helps in any way: http://jsfiddle.net/PnUmM/1/
I set the position to relative in the CSS, calculate where it is on document load to keep the info aside and then set it to fixed.
var sticky_offset;
$(document).ready(function() {
var original_position_offset = $('#sticky_for_a_while').offset();
sticky_offset = original_position_offset.top;
$('#sticky_for_a_while').css('position', 'fixed');
});
$(window).scroll(function () {
var sticky_height = $('#sticky_for_a_while').outerHeight();
var where_scroll = $(window).scrollTop();
var window_height = $(window).height();
if((where_scroll + window_height) > sticky_offset) {
$('#sticky_for_a_while').css('position', 'relative');
}
if((where_scroll + window_height) < (sticky_offset + sticky_height)) {
$('#sticky_for_a_while').css('position', 'fixed');
}
});

I made this up for you: http://jsfiddle.net/XCYFG/1/.
$(document).ready(function() {
window._div1 = $('#div1'); //selector is expensive
window._window = $(window);
$(window).scroll(function(e) {
_div1.css("top",
Math.min(_window.height(),
window.scrollY + 100)
+ _window.height() - _div1.height() - 110);
}).scroll();
});

I have a plugin that does the opposite - it's in the flow of the webpage, and when the user scrolls past it, it gets fixed to the viewport. What it actually does though is apply a css class to the element, so you should be able to use it as is.
You can find the plugin here:
https://github.com/hanssonlarsson/jquery-fixedscroll
Then I would suggest you have your element in the flow of your webpage:
<div id="sometimesFixed">content</div>
With css:
#sometimesFixed {
position: fixed;
bottom: 0;
}
#sometimesFixed.scroll {
position: static;
}
And apply the plugin like so, in your JavaScript:
$('#sometimesFixed').fixedscroll({className: 'scroll'});
There is also a more general plugin, very new, called jquery-waypoints. The idea is to bind any code to "waypoints", points on the webpage where, when the user scrolls past them, some code is executed.
https://github.com/imakewebthings/jquery-waypoints
It's probably more optimized and a better fit than my plugin, but YMMV!