Develop Reference

Changing the size of the image in the sticky header when scrolling down

On the website (please don't share), in WordPress, I set a sticky header using CSS
header#masthead {
position: sticky;
top: 0;
left: 0;
right: 0;
z-index: 10000;
}
This works correctly. However, the image in the header is too big, that's why I resized it with an animation when scrolling down
jQuery(document).ready(function() {
jQuery(function() {
var $nav = jQuery('#masthead .custom-logo');
var height_original = jQuery('#masthead .custom-logo').css("height").replace("px","");
var height_small = height_original * 0.666;
var width_original = jQuery('#masthead .custom-logo').css("width").replace("px","");
var width_small = width_original * 0.666;
jQuery(document).scroll( function() {
var value = jQuery(this).scrollTop();
if ( value > 0 ){
$nav.stop().animate({height:height_small,width:width_small},100);
} else if (value == 0 ) {
$nav.stop().animate({height:height_original,width:width_original},100);
}
});
});
});
But, it doesn't work properly.
I primarily use Opera GX, where it behaves like this - when scrolling down, the animation is slowed down. Also, if you just scroll down a little, the animation doesn't run all the way and the image goes back to its original size, scrolling up works without a problem.
The strange thing is that I've also tried it in Firefox, Chrome and Edge. It behaves differently in everyone, but nowhere does it work 100% correctly.
What is wrong with the code please?
Thank you

I think instead of that long jquery code you can use this simple javascript code with some css to get the results you want:
I hope this helps you to reach what you looking for :)
JS
// Add a class to the header when scrolling
let header = document.querySelector('header');
window.addEventListener('scroll' , function () {
let window_top = this.scrollY;
if (window_top == 0) {
header.classList.remove('resize');
}else {
header.classList.add('resize');
}
});
CSS
/* these are the default styles (when the user doesnt scroll down yet) */
header#masthead {
position: sticky;
top: 0;
left: 0;
right: 0;
z-index: 10000;
transition: .3s;
}
header#masthead img{
transition: .3s; /*here i added transition to give the image a smooth animation*/
}
/* these are the styles when the user scrolls */
header#masthead.resize img{
height: 50px; /* <=== here i gived the image a smaller size */
}

make div scoll untill it reaches top of page then fixed

let's get straight to the point:
My code looks like the following:
<div id="keep_up">
<div id="thread_menu">
<div id="new_thread">
</div>
</div>
</div>
And my css:
#keep_up {
position: fixed;
width: 13%;
}
#thread_menu{
height: 80vh;
width: 100%;
float: left;
position: relative;
}
Now i use this for a forum. and this is basically to show the active and new threads on the side of the screen.
However. When watching a thread, the header disappears (Wich makes sense because we are scrolling down).
but i want the thread menu to stay on my side (So that it is always visible). In this case that is happening because my keep_up div has position: fixed. But i only see half of the thread menu becuase it is too long and won't scroll up.
My question:
I want the thread menu to scroll up, untill it reaches the top of my window. From then on i want it to stay there.
How do i do this?
I saw a few examples but none of them worked for me.
EDIT: Code i tried:
<script src="jquery.min.js">
$(window).scroll(function () {
var margin = null;
$(window).on("scroll", function () {
var scrollHeight = $(document).height(),
scrollTop = $(window).scrollTop(),
offsetBottom = 110, // Offset depending on the height of the footer
offsetTop = 100, // Offset depending on the height of the header
positionTop = $(".keep_up").offset().top,
affix;
if (margin != null && (scrollTop + margin <= positionTop)) {
// The sidebar has reached the bottom and is still on the bottom
affix = false;
} else if (positionTop + $(".keep_up").height() >= scrollHeight - offsetBottom) {
// The sidebar has reached the bottom
affix = 'bottom';
} else if (scrollTop <= offsetTop) {
// The sidebar has reached the top
affix = 'top';
} else {
// The sidebar is midway
affix = false;
}
// If the sidebar hasnot changed his state, return;
if ($(".keep_up").hasClass('at' + (affix ? '-' + affix : ''))) return;
if (affix == 'bottom') {
margin = positionTop - scrollTop;
} else {
margin = null;
}
// If the related class is added to the div
$(".keep_up").removeClass('at at-top at-bottom').addClass('at' + (affix ? '-' + affix : ''))
});
});
</script>
And the CSS:
.keep_up{
/*position: fixed;*/
width: 13%;
}
.keep_up.at {
top: 1px;
position: fixed;
}
.keep_up.at-top{
}
.keep_up.at-bottom {
top: 438px;
position: absolute;
}

modify this on HTML:
<div id="prevent"></div>
<div id="keep_up" data-spy="affix" data-offset-top="200">
Add this CSS:
.affix{position: fixed !important; top:0px; z-index:999;}
.affixpatch{margin-top:100px !important;}
this will fix the div when you scroll down 200px. Change data-offset-top value to reach it on different break point.
.affixpatch is a class that will be loaded with next jquery function. it prevents to hide content behind top fixed div. Change margin-top to another value if this don't solves the "hide content" problem that always generate affixing divs.
<script>
$(function() {
//caches a jQuery object containing the header element
var header = $(".affix");
$(window).scroll(function() {
var scroll = $(window).scrollTop();
if (scroll >= 200) {
$('#prevent').addClass("affixpatch");
} else {
$('#prevent').removeClass("affixpatch");
}
});
});
</script>
Hope it helps. If not, you may have some class that rewrite or impede the correct function of this affix.
I've tested this hundreds of times, usually to fix navbars.
SCROLL:
Using overflow to scroll content:
#keep_up{
max-height:400px;
width: auto;
overflow:auto;}
This will scroll the content inside #keep_up div (or use it in another one)
NOTE: you must declare a fixed max height for this div. Set max-width only if you need.
You can use %, em, rem... no need to be px for fix the max witdth. (to get a responsive effect, use responsive measurements)

If I understand your scenario correctly, the way to do this might be to use jQuery (or native JS, but you've tagged jQuery so I'm assuming that's in play).
There's a plugin that handles this kind of thing: http://leafo.net/sticky-kit/
I'd suggest you look at the plugin source code to see how it works - an event handler function on $(window).scroll() which then toggles classes on your #thread_menu to fix it in place. To keep your code lightweight, you probably don't need everything the plugin provides.

A cleaner way for a fixed div at bottom of the window but stays above the footer and triggers on page width

I've created a sticky bar to stay at the bottom of the window. As the user scrolls down to the bottom of the page the same bar will stay fixed until the footer shows, then removes its fixed position, temporarily, to stay above the footer until the user scrolls back up and it remains fixed again.
I only want to happen when the page is wider than 680px. Anything under that will keep the sticky bar in a default position (CSS: position:inherit).
This is the website: http://ttd.firefly-digital.co.uk
It works as expected. However, when I test on Chrome in Mac it triggers my CPU fan which suggests this not very efficient and with my limited JavaScript skills, wondered if there is a cleaner way to achieve this is?
This is the current js code:
$(window).scroll(function(event) {
var scroll = $(this).scrollTop();
var docHeight = $(document).height();
var windowHeight = $(window).height();
var footerHeight = $('.footer').height();
if(docHeight - (windowHeight + scroll) < footerHeight) {
$('.contact-bar').css({
bottom: footerHeight - (docHeight - (windowHeight + scroll))
});
} else {
$('.contact-bar').css({
bottom: 0
});
}
});
var windowWidth = $(window).width();
$(window).resize(function() {
windowWidth = $(window).width();
if(windowWidth > 680) {
$('.contact-bar').css({
position: "fixed"
});
} else {
$('.contact-bar').css({
position: "inherit"
});
}
});
CSS code
.contact-bar {
background: $contact-bar;
width: 100%;
height: 40px;
text-align: center;
position: fixed;
bottom: 0;
z-index: 10;
}

You can do it in reverse. Make it so that the bar, without position fixed, is above the footer without any JavaScript (incl. media queries). Than add a fixed class with position:fixed and bottom:0 that will be added accordingly. Like so:
.contact-bar.fixed { position:fixed; bottom:0; }
The jquery code that will trigger this, is as follows:
$(window).scroll(function (event) {
var windowTop = $(this).scrollTop();
if (windowTop >= $(".footer").offset().top) {
$(".contact-bar").addClass("fixed");
} else {
$(".contact-bar").removeClass("fixed");
}
});
Then add a few lines that the above code will only fire if the window width is > 680, either with jquery or pure javascript. For example with:
if ($(window).width() < 960) { // above function }
Do note I have not tested this, so please comment if it doesn't work. Credit: Preventing element from displaying on top of footer when using position:fixed

You better use classes to target your elements, at least to prevent jQuery from traversing the whole DOM using selectors appropriately which is good in performance.

table needs to be fixed during scrolling

I have 3 tables and one of them I want to be fix after scroll more then specific distance
var distance = $("#thead").offset().top;
$(window).scroll(function () {
var wdistance = $(window).scrollTop();
if (wdistance > distance) {
};
})
demo jsfiddle
I want to say when this "if" is correct then position of div with "thead" id become fixed on top of the other tables when scrolling the page. and after the div with id "first" is finish then <div id="thead"></div> come back to previous place.

You can create a .fixed class and add/remove that to/from the #thead element, as follows:
CSS
* { padding: 0; margin: 0; } /* Tiny reset for removing paddings and margins */
.fixed {
position: fixed;
top: 0;
left: 0;
width: 100%;
}
Note that, you have to remove the padding/margin from the <body> element to adjust the width of each column (when the #thead is positioned).
Or use the same padding/margin for the positioned #thead element as well.
var $table = $("#thead"),
$window = $(window),
distance = $table.offset().top;
$window.scroll(function () {
var wdistance = $window.scrollTop();
if (wdistance > distance) {
$table.addClass('fixed');
} else {
$table.removeClass('fixed');
}
});
WORKING DEMO.

My sticky header causes the subsequent div to jump about 100 pixels when the navbar reaches the top of the page, can't figure out a fix?

As my title says, my sticky header is causing the subsequent div to jump about 100 pixels when the navbar reaches the top of the page. It's like the home div is magically losing 100 pixels of its height. I've tried a couple things but haven't been able to get this to work.
I have added plugins for smooth scrolling but couldn't get it to work in the jsfiddle. If you scroll down slowly when the navbar is getting to the top of the page, you will notice the skip.
Thanks for your help!
http://jsfiddle.net/g9N78/2/
here is the code I'm using for the sticky header:
<script>
function moveScroller() {
var move = function() {
var st = $(window).scrollTop();
var ot = $("#nav").offset().top;
var s = $(".nav");
if(st > ot) {
s.css({
position: "fixed",
top: "0",
background: "rgba(0,0,0,0.65)"
});
} else {
if(st <= ot) {
s.css({
position: "",
top: "",
background: "black"
});
}
}
};
$(window).scroll(move);
move();
}
</script>
<script type="text/javascript">
$(function() {
moveScroller();
});
</script>

Since you are removing that object from the DOM flow the space is available and the element under takes it, you can just add some margin to #home like this:
$('#home').css('marginTop','100px');
Check this Demo http://jsfiddle.net/g9N78/3/

Use the jQuery .height() method to find out the height of your nav bar, save it to a variable, then apply that height to the top margin of the page, to make it fill the space that the nav bar used to occupy.
$(".nav").height();
$('#home').css('marginTop', navHeight);
See the fiddle below...
http://jsfiddle.net/g9N78/8/
jQuery:
function moveScroller() {
var move = function() {
var st = $(window).scrollTop();
var ot = $("#nav").offset().top;
var s = $(".nav"),
navHeight = s.height();
if(st > ot) {
s.css({
position: "fixed",
top: "0",
background: "rgba(0,0,0,0.65)"
});
$('#home').css('marginTop', navHeight);
} else {
if(st <= ot) {
s.css({
position: "",
top: "",
background: "black"
});
}
$('#home').css('marginTop', '0');
}
};
$(window).scroll(move);
move();
}

There is no magic involved. As long as you do not reach the scroll-top, the header is position:static. The following div will be displayed under the Top. As soon as the element is set to position: fixed, you "lose" the height of the header, causig the optical jump.
I don't think you need Javascript for your header to be sticky.
Try removing the javascript and add this css:
body
{
padding-top: 90px;
}
.nav
{
position: fixed;
top: 0px;
height: 90px;
width: 100%;
}
Edit: Sorry I did not think about your Logo. So this will not work for you like that.