JQuery .scroll() event to show hidden object does not work - javascript

I'm using .scroll() in order to make the image #mag visible once I scroll past a certain point.
$(window).scroll(function() {
var y_scroll_pos = window.pageYOffset;
var scroll_pos_test = 1000;
if(y_scroll_pos > scroll_pos_test) {
$("#mag").css("visibility","visible");
}
});
<img id= "mag" src="assets/maginatransparent.png" style = "visibility: hidden; position: fixed; height: 40vh; bottom: 30vh; right: 0">
When I run this, I get no errors, but the event doesn't seem to have been triggered even when I scroll past 1000px.
JSFiddle Link: https://jsfiddle.net/k04qck9h/
Note this uses a span instead of an img.

You need to use $(window).scrollTop();
$(window).scroll(function() {
var y_scroll_pos = $(window).scrollTop();
var scroll_pos_test = 1000;
if(y_scroll_pos > scroll_pos_test) {
$("#mag").css("visibility","visible");
}else{
$("#mag").css("visibility","hidden");
}
});
DEMO

Related

CSS half page fixed half scroll not working smoothly

Using a code snippet I found online https://codepen.io/mattyfours/pen/LNgOWx
I made slight modifications and now, although the scroll/fixed functionality works, my 'fixed' side jumps when scrolling. I added 'background-size: contain' onto the fixed side which only works when scrolling has commenced However, on page load/ when no scrolling has occurred the image remains at its full-size meaning once scrolling begins the image goes from full width to 'contained' and created a jump.
Github:
https://github.com/tavimba/fixed-scroll
The issue can be seen in about.html
javascript:
var window_height;
var header_height;
var doc_height;
var posTop_sticky1;
var posBottom_sticky1;
var posTop_s2;
var posBottom_s2;
$(document).ready(function() {
getValues();
});
$(window).scroll(function(event) {
var scroll = $(window).scrollTop();
if (scroll < posTop_sticky1) {
$('.sticky').removeClass('fixy');
$('.sticky').removeClass('bottom');
}
if (scroll > posTop_sticky1) {
$('.sticky').removeClass('fixy');
$('.sticky').removeClass('bottom');
$('#sticky1 .sticky').addClass('fixy');
}
if (scroll > posBottom_sticky1) {
$('.sticky').removeClass('fixy');
$('.sticky').removeClass('bottom');
$('#sticky1 .sticky').addClass('bottom');
$('.bottom').css({
'max-height': window_height + 'px'
});
}
if (scroll > posTop_s2 && scroll < posBottom_s2) {
$('.sticky').removeClass('fixy');
$('.sticky').removeClass('bottom');
$('#s2 .sticky').addClass('fixy');
}
});
function getValues() {
window_height = $(window).height();
doc_height = $(document).height();
header_height = $('header').height();
//get heights first
var height_sticky1 = $('#sticky1').height();
var height_s2 = $('#s2').height();
//get top position second
posTop_sticky1 = header_height;
posTop_s2 = posTop_sticky1 + height_sticky1;
//get bottom position 3rd
posBottom_sticky1 = posTop_s2 - header_height;
posBottom_s2 = doc_height;
}
var rtime;
var timeout = false;
var delta = 200;
$(window).resize(function() {
rtime = new Date();
if (timeout === false) {
timeout = true;
setTimeout(resizeend, delta);
}
});
function resizeend() {
if (new Date() - rtime < delta) {
setTimeout(resizeend, delta);
} else {
timeout = false;
getValues();
}
}
CSS:
section {
width: 100%;
min-height: 100%;
float: left;
position: relative;
}
header {
width: 100%;
height: 5vw;
background-color: black;
float: left;
}
.sticky {
height: 100%;
width: 60%;
float: left;
position: absolute;
}
.sticky.fixy {
position: fixed;
top: 0;
left: 0;
}
.sticky.bottom {
position: absolute;
bottom: 0;
}
.green {
background-image: url(../imgs/front%20view.jpg);
background-size: cover;
}
.stickyBg {
background-image: url(../imgs/bonnets.jpg);
background-size: cover;
}
.scrolling {
float: right;
width: 50%;
padding: 20px;
h5 {
margin-left: 135px;
}
p {
margin-left: 135px;
font-size: 1em;
line-height: 1.5;
}
}
The jump is caused by change of position from absolute to fixed in combination with 100% height.
Besides, the above code has the following flaws:
Max-height assignment looks inconsistent.
JS assumes exactly two sections in HTML: #section1 and #s2. The third section won't work.
Window resize is handled incorrectly. The half-page-scroll logic consists of the two steps: CalculateVars and AdjustDOMElementPositions. For the smooth look these two actions have to be done in 3 cases: onDocumentLoad, onResize and onScroll.
Global vars.
Looks like, it needs some refactoring to get work ;)
<section class="js-half-page-scroll-section"><!-- Get rid of id -->
...
</section>
function halfPageScroll() {
let scrollTop, windowHeight, headerHeight; // and some other common vars
// Calculate vars
scrollTop = $(window).scrollTop();
//...
let repositionSection = function($section) {
let sectionHeight; // and some other vars related to current section
// Some logic
}
$('.js-half-page-scroll-section').each((i, el) => repositionSection($(el)));
}
$(document).ready(halfPageScroll);
$(window).scroll(halfPageScroll);
$(window).resize(halfPageScroll); // TODO: add some debounce wrapper with timeouts

Code not working correctly in Safari and responsive browsers

I have the following code which 'shows/hides' my navigation up off the top of the screen, and brings it down again.
jQuery(document).ready(function($){
var didScroll;
var lastScrollTop = 0;
var delta = 5;
var navbarHeight = $('nav').outerHeight(true);
$(window).scroll(function(event) { didScroll = true; });
setInterval(function() {
if (didScroll) {
hasScrolled();
didScroll = false;
}
}, 0);
function hasScrolled() {
if($( window ).width() > 768) {
var st = $(this).scrollTop();
if (Math.abs(lastScrollTop - st) <= delta)
return;
if (st > lastScrollTop) {
// Scroll Down
$('#screen-nav').removeClass('nav-down').addClass('nav-up');
} else {
$('#screen-nav').removeClass('nav-up').addClass('nav-down');
}
}
lastScrollTop = st;
}
});
css
#screen-nav {
position: fixed;
top: 0; left: 0; right: 0;
}
#screen-nav.nav-up { top: -100px; }
#screen-nav.nav-down { top: 0; }
The problem is that on the safari browser and when the screen changes from mobile size (<768px on all browsers) to screen size sometimes the .nav-up class gets added and the navigation doesn't show. But only when the user scrolls to the top of the page.
Not sure if there is a better way to write the code to ensure proper functionality.
I see you are using this example. He has the fiddle working well too. the only thing is that on browser resize nothing regarding show the nav is in place. You should be able to just add that separately.
$(window).resize(function(){
$('#screen-nav').removeClass('nav-up').addClass('nav-down')
});
I updated his original fiddle to reflect the addition of window resize handling.

Bootstrap fix div element on top and prevent resize

I want to fix a div element on the top by scrolling.
I have achieved this with the following code:
Javascript:
$(function () {
var msie6 = $.browser == 'msie' && $.browser.version < 7;
if (!msie6) {
var top = $('#betslip').offset().top - parseFloat($('#betslip').css('margin-top').replace(/auto/, 0));
$(window).scroll(function (event) {
// what the y position of the scroll is
var y = $(this).scrollTop();
// whether that's below the form
if (y >= top) {
// if so, ad the fixed class
$('#betslip').addClass('fixed');
} else {
// otherwise remove it
$('#betslip').removeClass('fixed');
}
});
}
CSS:
#betslip.fixed {
position: fixed;
top: 0;
}
HTML:
<div class="col-md-12" id="betslip">
...
</div>
The problem is that, while scrolling the div element is getting larger. How I can fix/prevent this?
Here is a screenshot after and before the scrolling:
By adding position: fixed; to #betslip it will ignore width of container. Try adding width: inherit; to #betslip.fixed

Stop fixed element scrolling at certain point?

I have a fixed position nav that fades in at a set scroll point.
I now need to stop it scrolling just before the page footer (about 400px from the bottom). I know the way to do this would be to change the position from fixed to absolute but I'm not sure how to implement that through jquery?
Live Example on the jsFiddle
jQuery:
var isVisible = false;
$(window).scroll(function(){
var shouldBeVisible = $(window).scrollTop()>1000;
if (shouldBeVisible && !isVisible) {
isVisible = true;
$('#floatingnav').fadeIn('slow');
} else if (isVisible && !shouldBeVisible) {
isVisible = false;
$('#floatingnav').fadeOut('fast');
}
});
CSS:
#floatingnav{
position: fixed;
top: 40px;
display: none;
}
Check if the bottom position of the navigation is below the footer top position. If this is the case, set a class or a specific css-prop.
$(window).scroll(function(){
var windowTopPos = $(window).scrollTop();
var footerTopPos = $('#footer').offset().top;
var navBottomPos = $('#floatingnav').offset().top + $('#floatingnav').outerHeight();
if(navBottomPos >= footerTopPos) {
$('#floatingnav').css('position', 'absolute');
}
});

Add/remove class with jquery based on vertical scroll?

So basically I'd like to remove the class from 'header' after the user scrolls down a little and add another class to change it's look.
Trying to figure out the simplest way of doing this but I can't make it work.
$(window).scroll(function() {
var scroll = $(window).scrollTop();
if (scroll <= 500) {
$(".clearheader").removeClass("clearHeader").addClass("darkHeader");
}
}
CSS
.clearHeader{
height: 200px;
background-color: rgba(107,107,107,0.66);
position: fixed;
top:200;
width: 100%;
}
.darkHeader { height: 100px; }
.wrapper {
height:2000px;
}
HTML
<header class="clearHeader"> </header>
<div class="wrapper"> </div>
I'm sure I'm doing something very elementary wrong.
$(window).scroll(function() {
var scroll = $(window).scrollTop();
//>=, not <=
if (scroll >= 500) {
//clearHeader, not clearheader - caps H
$(".clearHeader").addClass("darkHeader");
}
}); //missing );
Fiddle
Also, by removing the clearHeader class, you're removing the position:fixed; from the element as well as the ability of re-selecting it through the $(".clearHeader") selector. I'd suggest not removing that class and adding a new CSS class on top of it for styling purposes.
And if you want to "reset" the class addition when the users scrolls back up:
$(window).scroll(function() {
var scroll = $(window).scrollTop();
if (scroll >= 500) {
$(".clearHeader").addClass("darkHeader");
} else {
$(".clearHeader").removeClass("darkHeader");
}
});
Fiddle
edit: Here's version caching the header selector - better performance as it won't query the DOM every time you scroll and you can safely remove/add any class to the header element without losing the reference:
$(function() {
//caches a jQuery object containing the header element
var header = $(".clearHeader");
$(window).scroll(function() {
var scroll = $(window).scrollTop();
if (scroll >= 500) {
header.removeClass('clearHeader').addClass("darkHeader");
} else {
header.removeClass("darkHeader").addClass('clearHeader');
}
});
});
Fiddle
Pure javascript
Here's javascript-only example of handling classes during scrolling.
const navbar = document.getElementById('navbar')
// OnScroll event handler
const onScroll = () => {
// Get scroll value
const scroll = document.documentElement.scrollTop
// If scroll value is more than 0 - add class
if (scroll > 0) {
navbar.classList.add("scrolled");
} else {
navbar.classList.remove("scrolled")
}
}
// Use the function
window.addEventListener('scroll', onScroll)
#navbar {
position: fixed;
top: 0;
left: 0;
right: 0;
width: 100%;
height: 60px;
background-color: #89d0f7;
box-shadow: 0px 5px 0px rgba(0, 0, 0, 0);
transition: box-shadow 500ms;
}
#navbar.scrolled {
box-shadow: 0px 5px 10px rgba(0, 0, 0, 0.25);
}
#content {
height: 3000px;
margin-top: 60px;
}
<!-- Optional - lodash library, used for throttlin onScroll handler-->
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.js"></script>
<header id="navbar"></header>
<div id="content"></div>
Some improvements
You'd probably want to throttle handling scroll events, more so as handler logic gets more complex, in that case throttle from lodash lib comes in handy.
And if you're doing spa, keep in mind that you need to clear event listeners with removeEventListener once they're not needed (eg during onDestroy lifecycle hook of your component, like destroyed() for Vue, or maybe return function of useEffect hook for React).
Example throttling with lodash:
// Throttling onScroll handler at 100ms with lodash
const throttledOnScroll = _.throttle(onScroll, 100, {})
// Use
window.addEventListener('scroll', throttledOnScroll)
Add some transition effect to it if you like:
http://jsbin.com/boreme/17/edit?html,css,js
.clearHeader {
height:50px;
background:lightblue;
position:fixed;
top:0;
left:0;
width:100%;
-webkit-transition: background 2s; /* For Safari 3.1 to 6.0 */
transition: background 2s;
}
.clearHeader.darkHeader {
background:#000;
}
Its my code
jQuery(document).ready(function(e) {
var WindowHeight = jQuery(window).height();
var load_element = 0;
//position of element
var scroll_position = jQuery('.product-bottom').offset().top;
var screen_height = jQuery(window).height();
var activation_offset = 0;
var max_scroll_height = jQuery('body').height() + screen_height;
var scroll_activation_point = scroll_position - (screen_height * activation_offset);
jQuery(window).on('scroll', function(e) {
var y_scroll_pos = window.pageYOffset;
var element_in_view = y_scroll_pos > scroll_activation_point;
var has_reached_bottom_of_page = max_scroll_height <= y_scroll_pos && !element_in_view;
if (element_in_view || has_reached_bottom_of_page) {
jQuery('.product-bottom').addClass("change");
} else {
jQuery('.product-bottom').removeClass("change");
}
});
});
Its working Fine
Is this value intended? if (scroll <= 500) { ... This means it's happening from 0 to 500, and not 500 and greater. In the original post you said "after the user scrolls down a little"
In a similar case, I wanted to avoid always calling addClass or removeClass due to performance issues. I've split the scroll handler function into two individual functions, used according to the current state. I also added a debounce functionality according to this article: https://developers.google.com/web/fundamentals/performance/rendering/debounce-your-input-handlers
var $header = jQuery( ".clearHeader" );
var appScroll = appScrollForward;
var appScrollPosition = 0;
var scheduledAnimationFrame = false;
function appScrollReverse() {
scheduledAnimationFrame = false;
if ( appScrollPosition > 500 )
return;
$header.removeClass( "darkHeader" );
appScroll = appScrollForward;
}
function appScrollForward() {
scheduledAnimationFrame = false;
if ( appScrollPosition < 500 )
return;
$header.addClass( "darkHeader" );
appScroll = appScrollReverse;
}
function appScrollHandler() {
appScrollPosition = window.pageYOffset;
if ( scheduledAnimationFrame )
return;
scheduledAnimationFrame = true;
requestAnimationFrame( appScroll );
}
jQuery( window ).scroll( appScrollHandler );
Maybe someone finds this helpful.
For Android mobile $(window).scroll(function() and $(document).scroll(function() may or may not work. So instead use the following.
jQuery(document.body).scroll(function() {
var scroll = jQuery(document.body).scrollTop();
if (scroll >= 300) {
//alert();
header.addClass("sticky");
} else {
header.removeClass('sticky');
}
});
This code worked for me. Hope it will help you.
This is based of of #shahzad-yousuf's answer, but I only needed to compress a menu when the user scrolled down. I used the reference point of the top container rolling "off screen" to initiate the "squish"
<script type="text/javascript">
$(document).ready(function (e) {
//position of element
var scroll_position = $('div.mainContainer').offset().top;
var scroll_activation_point = scroll_position;
$(window).on('scroll', function (e) {
var y_scroll_pos = window.pageYOffset;
var element_in_view = scroll_activation_point < y_scroll_pos;
if (element_in_view) {
$('body').addClass("toolbar-compressed ");
$('div.toolbar').addClass("toolbar-compressed ");
} else {
$('body').removeClass("toolbar-compressed ");
$('div.toolbar').removeClass("toolbar-compressed ");
}
});
}); </script>

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