Develop Reference

jQuery scrollTop() returns wrong offset on scroll-direction change

I'm trying to get the correct scroll direction via jQuery's "scroll" event.
For this, I'm using the solution here: https://stackoverflow.com/a/4326907/8407840
However, if I change the direction of my scroll, the offset returned by scrollTop is incorrect on the first time. This results in the following behavior:
Wheel down -> down
Wheel down -> down
Wheel up -> down
Wheel up -> up
Wheel down -> up
Wheel down -> down
... and so on, I think you get it.
var ACTIVE_SECTION = null;
var ANIMATION_DURATION = 700;
$(document).ready(function() {
ACTIVE_SECTION = $("section:first-of-type").get(0);
var prevPosition = $(window).scrollTop();
$(window).on("scroll", function() {
doScrollingStuff(prevPosition);
});
});
function doScrollingStuff(prevPosition) {
var ctPosition = $(window).scrollTop();
var nextSection = ACTIVE_SECTION;
// Remove and re-append event, to prevent it from firing too often.
$(window).off("scroll");
setTimeout(function() {
$(window).on("scroll", function() {
doScrollingStuff(prevPosition);
});
}, ANIMATION_DURATION + 100);
// Determine scroll direction and target the next section
if(ctPosition < prevPosition) {
console.log("up");
nextSection = $(ACTIVE_SECTION).prev("section").get(0);
} else if(ctPosition > prevPosition) {
console.log("down");
nextSection = $(ACTIVE_SECTION).next("section").get(0);
}
// If a next section exists: Scroll to it!
if(typeof nextSection != 'undefined') {
var offset = $(nextSection).offset();
$("body, html").animate({
scrollTop: offset.top
}, ANIMATION_DURATION);
ACTIVE_SECTION = nextSection;
} else {
nextSection = ACTIVE_SECTION;
}
console.log(ACTIVE_SECTION);
prevPosition = ctPosition;
}
section {
width:100%;
height:100vh;
padding:60px;
box-sizing:border-box;
}
section:nth-child(1) { background:#13F399; }
section:nth-child(2) { background:#14FD43; }
section:nth-child(3) { background:#4EE61E; }
section:nth-child(4) { background:#BEFD14; }
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<section id="sect1">Section 1</section>
<section id="sect2">Section 2</section>
<section id="sect3">Section 3</section>
<section id="sect4">Section 4</section>
Here's a pen, where you can see my implementation: https://codepen.io/EigenDerArtige/pen/aVEyxd
I am trying to accomplish an autoscroll to the next or previous section, whenever the user scrolls or swipes up/down... Therefore I only fire the "scroll"-event once every second, to prevent multiple scrolljacks all happening at once... However the above behavior seems to result in the user being scrolled to the wrong section.
I've been trying for a couple of hours now to get it working, but to no avail. Help is greatly appreciated!

The problem lies in the assignment prevPosition = ctPosition.
Each time the scroll handler runs, var ctPosition = $(window).scrollTop(); is good for determining scroll direction, however it's not the value that should be rememberad as prevPosition.
prevPosition needs to be $(window).scrollTop() as measured after the animation has completed.
Try this :
$(document).ready(function() {
var ANIMATION_DURATION = 700;
var ACTIVE_SECTION = $("section:first-of-type").eq(0);
var prevPosition = $(window).scrollTop();
$(window).on("scroll", doScrollingStuff);
function doScrollingStuff(e) {
$(window).off("scroll");
var ctPosition = $(window).scrollTop();
var nextSection = (ctPosition < prevPosition) ? ACTIVE_SECTION.prev("section") : (ctPosition > prevPosition) ? ACTIVE_SECTION.next("section") : ACTIVE_SECTION; // Determine scroll direction and target the next section
// If next section exists and is not current section: Scroll to it!
if(nextSection.length > 0 && nextSection !== ACTIVE_SECTION) {
$("body, html").animate({
'scrollTop': nextSection.offset().top
}, ANIMATION_DURATION).promise().then(function() {
// when animation is complete
prevPosition = $(window).scrollTop(); // remember remeasured .scrollTop()
ACTIVE_SECTION = nextSection; // remember active section
$(window).on("scroll", doScrollingStuff); // no need for additional delay after animation
});
} else {
setTimeout(function() {
$(window).on("scroll", doScrollingStuff);
}, 100); // Debounce
}
}
});

jQuery: clone div multiple times on scroll

I'm trying to figure out how to repeatedly clone the contents of a div on scroll, thus giving the impression that the page goes on forever and ever. My markup thus far is as follows and a fiddle here too https://jsfiddle.net/guht49La/:
var inserated = false
$(window).scroll(function() {
var scroll = $(window).scrollTop();
if (scroll >= 800 && inserated == false) {
var $button = $('.hd').clone();
($button).insertBefore('.ap');
inserated = true;
} else {
}
});
Although this only inserts it once, as I want to keep inserting it every 800px (for example) thus giving the impression that the page goes on forever and ever. Any suggestions on this would be greatly appreciated!

This will work
var inserated = false
$(window).scroll(function() {
var scroll = $(window).scrollTop();
if (scroll >= 800) {
var $button = $('.hd').clone();
($button).insertBefore('.ap');
inserated = true;
} else {
}
});

This is a complete guess, but perhaps give this a go:
var nextInsert = 800;
$(window).scroll(function() {
var scroll = $(window).scrollTop();
if (scroll >= nextInsert) {
var $button = $('.hd').clone();
($button).insertBefore('.ap');
nextInsert += 800;
} else {
}
});

It is working, but it clones the div just once because you changed the inserated variable to true after inserting the first clone. It will work indefinitely if you delete it:
var inserated = false
$(window).scroll(function() {
var scroll = $(window).scrollTop();
if (scroll >= 800 && inserated == false) {
var $button = $('.hd').clone();
($button).insertBefore('.ap');
// inserated = true;
} else {
}
});
Notice that inserated = true; is commented out.
That code, however, can (and almost certainly) creates a huge amount of clones, so I'd suggest controlling the scrolling insertion point using something along the lines of Nat Karmios answer

My suggestion is similar to jbmartinez answer, except I would drop the inserated variable altogether and use classes to determine elements to be cloned:
$(window).scroll(function() {
var scroll = $(window).scrollTop();
if (scroll >= 800) {
var $button = $('.hd').not(".cloned").clone();
$button.addClass("cloned");
($button).insertBefore('.ap');
} else {
}
});
Would still need to adjust the scrolling mark as noted above tho.

Only execute JS if the screen size is more than 1024px?

I have a sidebar that becomes position:fixed when the bottom of the div is visible (followed this tutorial). My problem is I only need the JS to work if the screen size is more than or equal to 1025px.
I know I need something along the lines of if($(window).width() > 1025), but I can't figure out where that needs to be. I'm not great with JS so any help would be appreciated.
Demo
JS
$(function () {
if ($('.leftsidebar').offset()!=null) {
var top = $('.leftsidebar').offset().top - parseFloat($('.leftsidebar').css('margin-top').replace(/auto/, 0));
var height = $('.leftsidebar').height();
var winHeight = $(window).height();
var footerTop = $('#footer').offset().top - parseFloat($('#footer').css('margin-top').replace(/auto/, 0));
var gap = 100;
$(window).scroll(function (event) {
// what the y position of the scroll is
var y = $(this).scrollTop();
// whether that's below the form
if (y+winHeight >= top+ height+gap && y+winHeight<=footerTop) {
// if so, ad the fixed class
$('.leftsidebar').addClass('leftsidebarfixed').css('top',winHeight-height-gap +'px');
}
else if (y+winHeight>footerTop) {
// if so, add the fixed class
$('.leftsidebar').addClass('leftsidebarfixed').css('top',footerTop-height-y-gap+'px');
}
else
{
// otherwise remove it
$('.leftsidebar').removeClass('leftsidebarfixed').css('top','315px');
}
});
}
}

This should work:
var flag = false;
// This will keep on checking for window size while you are scrolling.
$(window).on("scroll", function() {
if (flag){
// Do whatever you want here
alert("hey");
}
});
$(window).on("resize", function() {
if ($(window).width() >= 1025){
flag = true;
} else {
flag = false;
}
})

From my comment: Just put that if($(window).width() > 1025) inside the function provided to the scroll event.
e.g.
$(window).scroll(function (event) {
if ($(window).width() > 1024) {
// what the y position of the scroll is
var y = $(this).scrollTop();
// whether that's below the form
if (y + winHeight >= top + height + gap && y + winHeight <= footerTop) {
// if so, ad the fixed class
$('.leftsidebar').addClass('leftsidebarfixed').css('top', winHeight - height - gap + 'px');
} else if (y + winHeight > footerTop) {
// if so, ad the fixed class
$('.leftsidebar').addClass('leftsidebarfixed').css('top', footerTop - height - y - gap + 'px');
JSFiddle: http://jsfiddle.net/TrueBlueAussie/3w5dt/31/
Notes:
not that 1 PX matters, but you did say > 1024px, hence changing 1025 to 1024 :)

First of all you should have a look at the jQuery documentation. The $.browser function was removed in jQuery 1.9. This can end up in serious problems in your code.
Just add something like the follwing code in the first if condition:
if (!msie6 && $('.leftsidebar').offset()!=null && $(window).width() > 1025 ) {
...
}
That should be all. If you want, that javascript should react on window resize just add something like the following
$(window).on('resize', function( event ) { /* code here */ }).trigger('resize');

if(screen.width >= 1024)
{
$(window).scroll(function (event) {
//Write your function code here
});
}
I hope it will help you.

Turning jQuery event listener on after off

So I want to turn off a jQuery event under a certain condition (if the user scrolls down) but if they do the opposite (scroll up) then I want the event turned to on so that it will fire.
This is my code but as I am new to jQuery, I am pretty sure I'm missing something in the handler - I just don't know what it should be.
Here is the code:
function myFunction() {
var handler = function(e){
//code here
}
var position = $(window).scrollTop();
$(window).scroll(function() {
var scroll = $(window).scrollTop();
if(scroll > position) {
// scrolling downwards
$(window).off("scroll", handler);
}
if(scroll < position) {
//scrolling upwards
$(window).on("scroll", handler);
hypeDocument.showPreviousScene(hypeDocument.kSceneTransitionPushTopToBottom, 1.1)
}
position = scroll;
});
}

try using an if-else statement instead of two ifs

$(function()
{
var handler = function(e){
// hypeDocument.showPreviousScene(hypeDocument.kSceneTransitionPushTopToBottom, 1.1)
console.log('handler');
}
var position = $(window).scrollTop();
$(window).scroll(function() {
var scroll = $(window).scrollTop();
if (scroll > position) {
// scrolling downwards
// NOTHING
}
if(scroll < position) {
//scrolling upwards
handler();
}
position = scroll;
});
});
Open console and you'll see "handler" in output each time you scroll up.
You need to add scroll handler after document.ready event:
$(function() {
/* YOUR CODE HERE */
});
I think you doing wrong trying to subscribe and unsubscribe your handler.
You should just determine the direction of scroll as you do.
Then if it is right direction – call your handler:
if (scroll < position) {
//scrolling upwards
handler();
}

Update 3: in future you could do this instead.
var nT = $(window).scrollTop, pos = nT(), func = function(e){ /*code here*/ };
$(window).scroll(()=>(nT()<pos)&&(pos=nT(),func())); //make people hate you.
Update 2: and to make it even smaller..
var newTop = $(window).scrollTop, position = newTop(),
handler = function(e){ /*code here*/ };
$(window).scroll(function() {
(newTop()<position)&&(position=newTop(),handler());
});
Update: Or you could make it even better
var newTop = $(window).scrollTop, position = newTop();
var handler = function(e){
//code here
};
$(window).scroll(function() {
var scroll = newTop();
if(scroll < position) handler();
position = scroll;
});
Use Boolean variable instead of attaching/detaching event.
var disabled= false,
newTop = $(window).scrollTop,
position = newTop();
var handler = function(e){
if (disabled) return;
//code here
};
$(window).scroll(function() {
var scroll = newTop();
if(scroll > position) disabled=true;
else disabled=false;
position = scroll;
});

Getting a floating div to stop upon reaching another div

I have a floating div on the sidebar that scrolls with the page. Is there a way to add code that makes it stop when it reaches the footer?
See code in action: http://openbayou.staging.wpengine.com
jQuery code used to float div:
$j=jQuery.noConflict();
$j(document).ready(function($) {
//this is the floating content
var $floatingbox = $('#one');
if($('#primary').length > 0){
var bodyY = parseInt($('#primary').offset().top) - 20;
var originalX = $floatingbox.css('margin-left');
$(window).scroll(function () {
var scrollY = $(window).scrollTop();
var isfixed = $floatingbox.css('position') == 'fixed';
if($floatingbox.length > 0){
$floatingbox.html();
if ( scrollY > 1561 && !isfixed ) {
$floatingbox.stop().css({
position: 'fixed',
top: 10,
});
} else if ( scrollY < 1561 && isfixed ) {
$floatingbox.css({
position: 'relative',
top: 0,
});
}
}
});
}
});

Why not just set the z-index of the sidebar behind the z-index of the footer?
EDIT: I didn't like the result of this so I went and made this work in jquery the way you want it...
try this for your scroll function:
$(window).scroll(function () {
floatingbox = $("#one");
if(floatingbox.length > 0){
//get our current scroll position
var scrollY = $(window).scrollTop();
//get the position of the tag cloud relative to the document
var contentY = ($("#sidebar .sidebar-tag-cloud").offset().top + $("#sidebar .sidebar-tag-cloud").outerHeight(false));
//calculate the largest possible top margin size before it starts to overlap the footer
var lastY = $("#footer").offset().top - $("#one").outerHeight(false);
//check if our scroll location is past the bottom of the tag cloud
if ( scrollY > contentY )
{
//check if the current top position is less than the maximum position
if(floatingbox.offset().top<lastY)
{
//keep scrolling
floatingbox.stop().animate({"marginTop":scrollY-contentY});
}else
{
//check if we have scrolled back up and have a space at the top
if(scrollY<floatingbox.offset().top)
{
floatingbox.stop().animate({"marginTop":scrollY-contentY});
}else
{
// hard set to the maximum position
floatingbox.stop().css({"marginTop":lastY-contentY});
}
}
}
}
});
I also made it a little more dynamic by getting the location of the bottom of the tag cloud and using that instead of your hard-coded number.

Alright, after looking at your latest jsfiddle. I have modified that code to work with yours. http://jsfiddle.net/Tgm6Y/4430/ This will not have the animate lag and should work well for you.
$('#one').followTo('#two','#pointFive');
just replace #two with #footer and #pointFive with "#sidebar .sidebar-tag-cloud" and this should work in your code.

UPDATE: Found a solution to my problem.
$(function () {
var msie6 = $.browser == 'msie' && $.browser.version < 7;
if (!msie6) {
var top = $('#one').offset().top;
$(window).scroll(function (event) {
var y = $(this).scrollTop() + 20;
if (y >= top) {
$('#one').addClass('fixed');
}
else {
$('#one').removeClass('fixed');
}
// don't overlap the footer - pull sidebar up using a negative margin
footertotop = ($('#footer').position().top);
scrolltop = $(document).scrollTop() + 760;
difference = scrolltop - footertotop;
if (scrolltop > footertotop) {
$('#one').css('margin-top', 0 - difference);
}
else {
$('#one').css('margin-top', 0);
}
});
}
});
What this does is it stops before the footer and I can configure the stopping point.
I appreciate all the help in solving my problem!