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jQuery -- Prevent User from Scrolling Up Past Certain Scroll Height

I am making a one-page website.
Basically, I have this animated landing page with a landing image and a bootstrap jumbotron. I want to be able to implement a function where once the user scrolls past the end of the jumbotron, the user cannot scroll back up to view the landing image and the jumbotron. In a sense, either hide or delete the <div>s that were at the top, or completely disable scrolling back to those points.
I found this code, but it automatically disables scrolling up to the page top (after 200 px) on page load:
$(function() {
var scrollPoint = 200;
$(window).scroll(function() {
$(window).scrollTop() < scrollPoint ?
$(window).scrollTop(scrollPoint) : '';
}).scroll();
});
Any ideas?

You can use this code to hide the jumbotron.
$(window).bind('scroll', function() {
if($(window).scrollTop() >= $('#id_of_jumbotron').offset().top +
$('#id_of_jumbotron').outerHeight() - window.innerHeight) {
hideTheJumboTron();
}
});

try this:
$(function () {
var scrollPoint = 200;
$(window).scroll(function () {
if ($(window).scrollTop() < scrollPoint) {
console.log($(window).scrollTop());
$(window).scrollTop(scrollPoint)
return false;
}
}).scroll();
});

Scroll event only fire when scrolling top

I have a scroll function. It needs to alert when you scroll to bottom. Strangely, it only alerts when you scroll to top. What is the correct way to make it work when you scroll at bottom.
$(window).scroll(function() {
if ($(window).scrollTop() == $(document).height() - $(window).height()){
alert();
});
});

You can use a flag to keep the current scroll or update it and then check the current position:
$(function () {
cur = $(window).scrollTop();
$(window).scroll(function() {
if ($(window).scrollTop() < cur) {
// Scrolled Up!
} // Remove the extra `);` here.
});
});

try this
$(window).scroll(function() {
if ($(window).scrollTop() == $(document).height() - $(window).height()){
alert();
} //Remove from here
});
Remove ) after the end of if block.

Some issues with a 'scroll to top button'

I have this 'scroll to top button' that pops up after the user has scrolled down 300px. Everything works fine so far. What I'm trying to do now, is to make this button pop up at a specific element.
Here is the jQuery:
// hide #back-top first
$("#back-top").hide();
// fade in #back-top
$(function () {
$(window).scroll(function () {
if ($(this).scrollTop() > 100) {
$('#back-top').fadeIn();
} else {
$('#back-top').fadeOut();
}
});
// scroll body to 0px on click
$('#back-top a').click(function () {
$('body,html').animate({
scrollTop: 0
}, 800);
return false;
});
});
Ok, I then changed this line
if ($(this).scrollTop() > 100) {
to
if ($(this).scrollTop() > '.show-button-here') {
but it didn't work. Any ideas what I'm doing wrong?
Here is a fiddle: http://jsfiddle.net/v70L4buk/

You need to get the position of the element from the top of the page and then subtract how far from the top you want that element to get before showing the up arrow. In this case, I am showing the arrow when a link I created in the page gets to 300px from the top. Or you can remove the number and when that element gets to the top of the viewport the function will kick in.
if ($(this).scrollTop() > $('.show').offset().top - 300) {
JSFIDDLE: https://jsfiddle.net/gvpLe06c/1/

fadeOut on scroll at pixel height

i'm trying to achieve a Scroll to Top button that fades in at a certain point on the page and fades out at a certain point...I have the fadeIn function working properly but can't seem to get the proper syntax for the click event fadeOut; it just disappears once you get to the top, instead of fading out if you're <= 675px. Any help is greatly appreciated!
HTML:
</div>
BACK TO LOGIN
</div>
jQuery:
$(document).ready(function() {
//Check to see if the window is top if not then display button
$(window).scroll(function() {
if ($(this).scrollTop() > 675) {
$('.scrollToTop').fadeIn(500);
} else {
$('.scrollToTop').fadeOut(500);
}
});
//Click event to scroll to top
$('.scrollToTop').click(function() {
$('html, body').animate({
scrollTop : 0
}, 800);
return false;
});
});

I think your question isn't so clear but maybe you mean that when click on the scrollToTop button it doesn't disappear until the scroll reach to top of page, it's because when your animation function is running the .scroll can't runs so fast that disappear button when reach to 675px but you can fadeout button as soon as click on it using this code:
jQuery: $(document).ready(function() {
var isClicked = false;
$('.scrollToTop').css("display","none");
$(window).scroll(function() {
if (isClicked == false){
if ($(this).scrollTop() > 675) {
$('.scrollToTop').fadeIn(500);
} else {
$('.scrollToTop').fadeOut(500);
}
}
});
$('.scrollToTop').click(function() {
isClicked = true;
$('.scrollToTop').fadeOut(500);
$('html, body').animate({
scrollTop : 0
}, 800, function(){
isClicked = false;
});
});
});
The isClicked variable is added to prevent blinking button (you can remove it to figure out what i'm saying).
Also i add this line:
$('.scrollToTop').css("display","none");
because it seems that you don't need a "Scroll To Top" button when page load for first time and you are on the top of page.
Check JSFiddle Demo

Show A Sticky Bar Until User Scrolls Down to a <div>

I want to add a sticky bar at bottom of my page and I want it to fade out once user reaches to a div by scrolling and again fade in once user scrolls up and that div is not on screen anymore.
And it shouldn't show if user screen is big enough to show that div normally.
Please guys help me...
I am currently using this code:-
<script type="text/javascript">
//<![CDATA[
$(window).bind("scroll", function() {
if ($(this).scrollTop() > -1) { //Fade in at a level of height
$("#bottbar").fadeIn();
checkOffset();
} else {
$("#bottbar").stop().fadeOut();
}
});
function checkOffset() {
if($('#bottbar').offset().top + $('#bottbar').height() >= $('#stopDiv').offset().top) {
$('#bottbar').css('position', 'absolute');
}
if($(window).scrollTop() + $(window).height() < $('#stopDiv').offset().top) {
$('#bottbar').css('position', 'fixed'); // restore when you scroll up
}
}
//]]>
</script>
but it is not working as expected on my site bookaire.com
I am not sure whats the problem is with this code, it doesn't show the bar when site loads, it show only when user scrolls a little and when it reaches the stopdiv instead of hiding the bar it get stuck at center of screen.

Whew! that took me a while since I'm still a beginner with javascript but I think I got it.
Note: the bar is getting stuck in the middle on certain screen size because you are only changing the position from fixed to absolute in your javascript. instead, change the display from block to hidden.Also note that the css for #bottbar should already be display:block
I believe your requirements are:
1. it shouldn't show if user screen is big enough to show that div normally
2. to fade out once user reaches to a div by scrolling
See: JSFIDDLE
$(document).ready(function() {
if($(window).height() > $('#stopDiv').offset().top) {
$("#bottbar").css('display', 'none');
}
else {
$("#bottbar").css('display', 'block');
}
});
$(window).bind("scroll", function() {
if($(window).height() > $('#stopDiv').offset().top) {
$("#bottbar").css('display', 'none');
}
if ($(this).scrollTop() > -1) { //Fade in at a level of height
$("#bottbar").css('display', 'block');
checkOffset();
}
else {
$("#bottbar").css('display', 'none');
}
});
function checkOffset() {
if($('#bottbar').offset().top + $('#bottbar').height() >= $('#stopDiv').offset().top) {
$('#bottbar').css('display', 'none');
}
if($(window).scrollTop() + $(window).height() < $('#stopDiv').offset().top) {
$('#bottbar').css('display', 'block'); // restore when you scroll up
}
}