Develop Reference

How can i show/hide image with scrollTop

I've got a logo image that in page load is hidden. I'd like that the image would show after page scroll.
Tried that approach:
CSS:
#logo {
display: none;
}
JS/JQuery:
jQuery( document ).ready(function( $ ) {
$(document).scroll(function() {
var scroll = $(this).scrollTop();
if (scroll >=100){
$('#logo').show();
} else {
$('#logo').hide();
}
});
});
Case 1: if page is loaded with scroll = 0, after page scroll logo image doesn't show.
Case 2: if page is loaded with scroll > 100, logo image is show or hidden correctly.

Your code seems to work fine on scroll. If you just need to also conditionally hide/show the image based on the scroll position when the page loads, you can call the hide/show code when the page loads as well as when you scroll the page.
jQuery(document).ready(function($) {
function hideShow(scroll) {
if (scroll >= 100) {
$('#logo').show();
} else {
$('#logo').hide();
}
}
hideShow($(this).scrollTop());
$(document).scroll(function() {
hideShow($(this).scrollTop());
});
});
body {
height: 500vh;
}
#logo {
display: none;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<img src="http://kenwheeler.github.io/slick/img/fonz1.png" id="logo">

Run Jquery only when an element is in the viewport

I'm trying to perform the Jquery function below when the element becomes visible in the viewport rather than on the page load. What would I need to change to allow that to happen? I'm using an external JS file to perform the Jquery, so keep that in mind.
Here's a piece of the HTML that is associated with the Jquery function -
<div class="skillbar clearfix " data-percent="70%">
<div class="skillbar-title" style="background: #FF704D;">
<span>Illustrator</span></div>
<div class="skillbar-bar" style="background: #FF704D;"></div>
<div class="skill-bar-percent">70%</div>
</div>
jQuery(document).ready(function(){
jQuery('.skillbar').each(function(){
jQuery(this).find('.skillbar-bar').animate({
width:jQuery(this).attr('data-percent')
},4000);
});
});

I once came across such problem and what I used is waypoints small library.
all you need is to include this library and do:
var waypoint = new Waypoint({
element: document.getElementById('waypoint'),
handler: function(direction) {
console.log('Element is in viewport');
}
})

Using CSS3 transitions instead of jQuery animations might be more performant and simpler. a cheap and nasty way of pushing it out of screen to demonstarate the effect.
There's a couple of things you'll need to do - firstly if you only want the animation to trigger when it's in the viewport then you'll need to check if anything is in the viewport on scroll. Then only update the bars width when it comes into view. If you want the effect to repeat every time it comes into viewport you'll need to set .skillbar-bar's width back to 0 if it's out of the viewport (just add an else statement to the viewport checking if)
I've added a 1000px margin-top and 400px margin-bottom in my example to .skillbar as a cheap and nasty way of demonstrating the effect
(function($){
$(document).ready(function(){
var $els = $('.skillbar'); // Note this must be moved to within event handler if dynamically adding elements - I've placed it for performance reasons
var $window = $(window);
$window.on('scroll', function(){
$els.each(function(){ // Iterate over all skillbars
var $this = $(this);
if($window.scrollTop() > $this.offset().top - $window.height()){ // Check if it's in viewport
$this.find('.skillbar-bar').css({'width' : $this.attr('data-percent')}); // Update the view with percentage
}
});
});
});
}(jQuery));
.skillbar{
margin-top: 1000px;
margin-bottom: 400px;
position: relative
}
.skillbar-bar{
transition: width 4s;
position: absolute;
height: 20px;
}
.skill-bar-percent{
position: absolute;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
Scroll down 1000px :)
<div class="skillbar clearfix " data-percent="70%">
<div class="skillbar-title">
<span>Illustrator</span></div>
<div class="skillbar-bar" style="background: #FF704D; width: 20%"></div>
<div class="skill-bar-percent">70%</div>
</div>

This might work for you.
var el = $('.yourElement'),
offset = el.offset(),
scrollTop = $(window).scrollTop();
//Check for scroll position
if ((scrollTop > offset.top)) {
// Code..
}

Finding where element meets top of scrollable div

I have a scrollable div container fits multiple "pages" (or div's) inside of it's container.
My goal is to, at any given moment, figure out where inside my red container does it reach the top of my scrollable container. So it can be a constant on scroll event, or a button that triggers this task.
So for example. If I have a absolute div element inside one of my red boxes at top:50px. And if I scroll to where that div element reaches the top of my scrollable container. The trigger should say that I am at 50px of my red container.
I'm having a hard time grasping how to accomplish this but I've tried things like:
$("#pageContent").scroll(function(e) {
console.log($(this).scrollTop());
});
But it doesn't take into account the separate pages and I don't believe it it completely accurate depending on the scale. Any guidance or help would be greatly appreciated.
Here is my code and a jsfiddle to better support my question.
Note: If necessary, I use scrollspy in my project so I could target which red container needs to be checked.
HTML
<div id="pageContent" class="slide" style="background-color: rgb(241, 242, 247); height: 465px;">
<div id="formBox" style="height: 9248.627450980393px;">
<div class="trimSpace" style="width: 1408px; height: 9248.627450980393px;">
<div id="formScale" style="width: 816px; -webkit-transform: scale(1.7254901960784315); display: block;">
<form action="#" id="XaoQjmc0L51z_form" autocomplete="off">
<div class="formContainer" style="width:816px;height:1056px" id="xzOwqphM4GGR_1">
<div class="formContent">
<div class="formBackground">
<div style="position:absolute;top:50px;left:100px;width:450px;height:25px;background-color:#fff;color:#000;">When this reaches the top, the "trigger" should say 50px"</div>
</div>
</div>
</div>
<div class="formContainer" style="width:816px;height:1056px" id="xzOwqphM4GGR_2">
<div class="formContent">
<div class="formBackground"><div style="position:absolute;top:50px;left:100px;width:450px;height:25px;background-color:#fff;color:#000;">This should still say 50px</div></div>
</div>
</div>
</form>
</div>
</div>
</div>
</div>
CSS
#pageContent {
position:relative;
padding-bottom:20px;
background-color:#fff;
z-index:2;
overflow:auto;
-webkit-overflow-scrolling: touch;
-webkit-transform: translate(0, 0);
-moz-transform: translate(0, 0);
-ms-transform: translate(0, 0);
transform: translate(0, 0);
}
#formBox {
display: block;
position: relative;
height: 100%;
padding: 15px;
}
.trimSpace {
display: block;
position: relative;
margin: 0 auto;
padding: 0;
height: 100%;
overflow: hidden;
}
#formScale::after {
display: block;
content:'';
padding-bottom:5px;
}
#formScale {
position:relative;
width:816px;
margin:0;
-webkit-transform-origin: 0 0;
-moz-transform-origin: 0 0;
transform-origin: 0 0;
-ms-transform-origin: 0 0;
}
.formContainer {
position:relative;
margin : 0 auto 15px auto;
padding:0;
}
.formContent {
position:absolute;
width:100%;
height:100%;
}
.formBackground {
width:100%;
height:100%;
background-color:red;
}
JS
var PAGEWIDTH = 816;
$(window).resize(function (e) {
zoomProject();
resize();
});
function resize() {
$("#pageContent").css('height', window.innerHeight - 45 + 'px');
}
function zoomProject() {
var maxWidth = $("#formBox").width(),
percent = maxWidth / PAGEWIDTH;
$("#formScale").css({
'transform': 'scale(' + percent + ')',
'-moz-transform': 'scale(' + percent + ')',
'-webkit-transform': 'scale(' + percent + ')',
'-ms-transform': 'scale(' + percent + ')'
});
$(".trimSpace").css('width', (PAGEWIDTH * percent) + 'px');
$("#formBox, .trimSpace").css('height', ($("#formScale").height() * percent) + 'px');
}
zoomProject();
resize();
EDIT:
I don't think I am conveying a good job at relaying what I want to accomplish.
At the moment there are two .formContainer's. When I scroll #pageContainer, the .formContainer divs move up through #pageContainer.
So what I want to accomplish is, when a user clicks the "ME" button or #click (as shown in the fiddle below), I'd like to know where in that particular .formContainer, is it touching the top of #pageContainer.
I do use scroll spy in my real world application so I know which .formContainer is closest to the top. So if you just want to target one .formContainer, that is fine.
I used these white div elements as an example. If I am scrolling #pageContainer, and that white div element is at the top of screen as I am scrolling and I click on "ME", the on click trigger should alert to me that .formContainer is touching the top of #pageContainer at 50px from the top. If, the the red container is just touching the top of #pageContainer, it should say it is 0px from the top.
I hope that helps clear up some misconception.
Here is an updated jsfiddle that shows the kind of action that I want to happen.

I am giving this a stab because I find these things interesting. It might just be a starting point since I have a headache today and am not thinking straight. I'd be willing to bet it can be cleaned up and simplified some.
I also might be over-complicating the approach I took, getting the first visible form, and the positioning. I didn't use the getBoundingClientRect function either.
Instead, I approached it trying to account for padding and margin, using a loop through parent objects up to the pageContent to get the offset relative to that element. Because the form is nested a couple levels deep inside the pageContent element you can't use position(). You also can't use offset() since that changes with scroll. The loop approach allowed me to factor the top margin/padding in. I haven't looked at the other solutions proposed fully so there might be a shorter way to accomplish this.
Keeping in mind that the scale will affect the ACTUAL location of the child elements, you have to divide by your scale percentage when getting the actual location. To do that I moved the scalePercentage to a global var so it was usable by the zoom function and the click.
Here's the core of what I did. The actual fiddle has more logging and junk:
var visForm = getVisibleForm();
var formTop = visForm.position().top;
var parents = visForm.parentsUntil('#pageContent');
var truOffset = 0;
parents.each(function() {
truOffset -= $(this).position().top;
});
// actual location of form relative to pageContent visible pane
var formLoc = truOffset - formTop;
var scaledLoc = formLoc / scalePercent;
Updated Fiddle (forgot to account for scale in get func): http://jsfiddle.net/e6vpq9c8/5/

If I understand your question correctly, what you want is to catch when certain descendant elements reach the top of the outer container, and then determine the position of the visible "page" (div with class formContainer) relative to the top.
If so, the first task is to mark the specific elements that could trigger this:
<div class='triggerElement' style="position:absolute;top:50px;left:100px;width:450px;height:25px;background-color:#fff;color:#000;">When this reaches the top, the "trigger" should say 50px"</div>
Then the code:
// arbitrary horizontal offset - customize for where your trigger elements are placed horizontally
var X_OFFSET = 100;
// determine once, at page load, where outer container is on the page
var outerContainerRect;
$(document).ready(function() {
outerContainerRect = $("#pageContent").get(0).getBoundingClientRect();
});
// when outer container is scrolled
$("#pageContent").scroll(function(e) {
// determine which element is at the top
var topElement = $(document.elementFromPoint(outerContainerRect.left+X_OFFSET, outerContainerRect.top));
/*
// if a trigger element
if (topElement.hasClass("triggerElement")) {
// get trigger element's position relative to page
console.log(topElement.position().top);
}
*/
var page = topElement.closest(".formContainer");
if (page.length > 0) {
console.log(-page.get(0).getBoundingClientRect().top);
}
});
EDIT: Changed code to check formContainer elements rather than descendant elements, as per your comment.
http://jsfiddle.net/j6ybgf58/23/
EDIT #2: A simpler approach, given that you know which formContainer to target:
$("#pageContent").scroll(function(e) {
console.log($(this).scrollTop() - $("#xzOwqphM4GGR_1").position().top);
});
http://jsfiddle.net/rL4Ly3yy/5/
However, it still gives different results based on the size of the window. This seems unavoidable - the zoomProject and resize functions are explicitly resizing the content, so you would have to apply the inverse transforms to the number you get from this code if you want it in the original coordinate system.

I do not fully understand what it is that you are needing, but if i am correct this should do the trick
$("#pageContent").scroll(function(e) {
// If more then 50 pixels from the top has been scrolled
// * if you want it to only happen at 50px, just execute this once by removing the scroll listener on pageContent
if((this.scrollHeight - this.scrollTop) < (this.scrollHeight - 50)) {
alert('it is');
}
});
ScrollHeight is the full height of the object including scrollable pixels.
ScrollTop is the amount of pixels scrolled from the top.

You can use waypoints to detect the position of divs based on where you're scrolling.
Here is a link to their official website's example: http://imakewebthings.com/waypoints/shortcuts/inview/

Bring an element to top of the page even if the page does not scroll

Background:
Let's say you have a simple page which has a logo and a heading only and one paragraph
<img src="http://blog.stackoverflow.com/wp-content/uploads/StackExchangeLogo1.png">
<h1>Foo Bar</h1>
<p>ABC12345</p>
This is how that looks like
That page, obviously would not have vertical overflow / scroll bar for almost even tiny scale mobile devices, let alone computers.
Question
How can you bring that heading to the top left of the screen and move the logo out of focus unless someone scrolls up? Open to using any JavaScript library and any CSS framework
Attempts:
Tried using anchors but they only work if the page already had a scroll bar and anchor was out of focus.
Tried window.scrollTo but that also requires the page to have scroll already
Tried $("html, body").animate({ scrollTop: 90}, 100); but that also doesn't work when the page doesn't have overflow
Notes:
Please note that adding some extra <br/> to induce an overflow is not the way to go, it can be done that way but that's a very ordinary workaround
Why is it needed?
Its for a form for mobile devices, simple requirement is to take the first field of the form to top of the page and hide the logo (one can scroll up if they wish to see it) so it doesn't take attention away. Not using jQueryMobile for this particular task.

If you want the user to be able to scroll up and see the logo, then the logo must be within the top boundary of the body tag, because anything outside of that tag will not be viewable. This means you cannot use negative margins or offsetting like that. The only way to achieve this is to have the page scroll to the desired location that is within the top boundary of the body tag. You can set the time for this event to one millisecond, but there will still be a 'jump' in the page when it is loaded. So, the logic is: first make sure the page is long enough to scroll to the right place, then scroll there.
//Change the jQuery selectors accordingly
//The minimum height of the page must be 100% plus the height of the image
$('body').css('min-height',$(document).height() + $('img').height());
//Then scroll to that location with a one millisecond interval
$('html, body').animate({scrollTop: $('img').height() + 'px'}, 1);
View it here.
Alternatively, you can load the page without the image in the first place. Then your form field will be flush with the top of the document. Then you could create the element at the top and similarly scroll the page again. This is a round-a-bout way of doing the same thing though. And the page will still 'jump,' there is no way around that.

Only CSS and anchor link solution
With a pseudo element :
--- DEMO ---
First :
set : html,body{height:100%;}
Second :
Choose one of your existing tags. This tag mustn't have a relatively positioned parent (except if it is the body tag). Preferably the first element in the markup displayed after the logo. For your example it would be the h1 tag. And give it this CSS :
h1:before {
content:"";
position:absolute;
height:100%;
width:1px;
}
This creates an element as heigh as the viewport area. As it is displayed under the logo, the vertical scroll lenght is the same as the logo height.
Third :
Give the first element after logo an id (for this example I gave id="anchor").
Then you can use a link like this your_page_link#anchor and you will automaticaly scroll to the anchor (logo outside/above the viewport).
This works whatever height the logo is.
link to editable fiddle
Full code :
HTML
<img src="http://blog.stackoverflow.com/wp-content/uploads/StackExchangeLogo1.png">
<h1 id="anchor">Foo Bar</h1>
<p>ABC12345</p> Anchor link
CSS
html, body {
height:100%;
margin:0;
padding:0;
}
h1:before {
content:"";
position:absolute;
width:1px;
left:0;
height:100%;
}

You might need to add js functionality to hide the logo if user scrolls down but I guess following code will fullfill the first requirement.
Please see
<script src="js/jquery.js"></script>
<img id='logo' src="http://blog.stackoverflow.com/wp-content/uploads/StackExchangeLogo1.png" style="display:none">
<h1>Foo Bar</h1>
<p>ABC12345</p>
<script type="text/javascript">
var p = $( "p:first" );
var isScrolled=false;
/* For Firfox*/
$('html').on ('DOMMouseScroll', function (e) {
isScrolled = true;
if(p.scrollTop()==0 && isScrolled==true){
$('#logo').css('display','block');
}
});
/* For Chrome, IE, Opera and Safari: */
$('html').on ('mousewheel', function (e) {
isScrolled = true;
if(p.scrollTop()==0 && isScrolled==true){
$('#logo').css('display','block');
}
});
</script>
I have referred this question to find solution.

You could use touchmove event to detect swipe up or down. This is my example. You can try it on mobile device.
<style>
#logo {
position: absolute;
top: -100%;
-webkit-transition: top 0.5s;
-moz-transition: top 0.5s;
-ms-transition: top 0.5s;
-o-transition: top 0.5s;
transition: top 0.5s;
}
#logo.show {
top: 0;
}
</style>
<script>
var perY;
var y;
$(window).on('touchmove', function(e) {
e.preventDefault();
y = window.event.touches[0].pageY;
if(!perY)
perY = y;
else
{
if(y > perY)
$('#logo').addClass('show');
else
$('#logo').removeClass('show');
perY = null;
}
});
</script>
<img id="logo" src="http://blog.stackoverflow.com/wp-content/uploads/StackExchangeLogo1.png">
<h1>Foo Bar</h1>
<p>ABC12345</p>

This is the same problem i've encountered hiding the addressbar without the page overflowing. The only solution that fitted my needs was the following:
Set the min-height of the body to the viewportheight + your logo.
$('body').css('min-height', $(window).height() + 200);

This is a simple solution of getting the height of the contents to see if we can scroll to the part of the header, if not, we add height to the paragraph.
<img id="img" src="http://blog.stackoverflow.com/wp-content/uploads/StackExchangeLogo1.png" />
<h1 id="h" >Foo Bar</h1>
<p id="par" style="background:yellow;">
hello world
</p>
script:
function hola(){
var imgH = $("#img").outerHeight(true);
var titleH = $("#h").outerHeight(true);
var winH = $(window).height();
var parH = $('#par').outerHeight(true);
var contH = (imgH + titleH + parH);
var wishH = (imgH + winH);
console.log("wished height: " + wishH);
console.log("window height: " + winH);
console.log("content height: " + contH);
if(contH < wishH){
console.log("window is smaller than desired :(");
var newH = wishH - contH;
$("#par").height(parH + newH);
$(window).scrollTop(imgH);
}
}
Here is the working example:
http://jsfiddle.net/Uup62/1/

You may like this solution: http://jsfiddle.net/jy8pT/1/
HTML:
<div class="addScroll"></div>
<h1 class="logo"><img src="https://drupal.org/files/images/OQAAAI1PPrJY0nBALB7mkvju3mkQXqLmzMhxEjeb4gp8aujEUQcLfLyy-Sn4gZdkAas6-k8eYbQlGDE-GCjKfF5gIrUA15jOjFfLRv77VBd5t-WfZURdP9V3PdmT.png" height="100" alt="company logo"/></h1>
<h2>This is a sample page heading.</h2>
<p>This is a sample page text.</p>
JS:
function addScroll()
{
$(".addScroll").css({
"height": ($(window).height()+1) + "px",
"width": "100%"
});
}
$(document).ready(function(){
addScroll();
$(window).resize(function(){
addScroll();
});
$(window).scroll(function(){
if($(window).scrollTop() > 0)
{
$(".logo").animate({
marginTop: "-110px"
}, 500);
}
if($(window).scrollTop() == 0)
{
$(".logo").animate({
marginTop: "0"
}, 500);
}
});
});
CSS:
body
{
padding:0;
margin:0;
}
h1.logo
{
display:block;
margin:0 0 10px 0;
padding:0;
outline:0;
}
.addScroll
{
position:absolute;
display:block;
top:0;
left:0;
z-index:-1;
}

Why does my JS code act so intermittently?

The JS code below is meant to get the height of the browser and the height of the .banner div. If the banner height is greater than the browser height, append two divs (.title and .social) to the body otherwise don't do anything and leave .title and .social divs where they are.
I'm also wanting the .title and .social divs to fade out when a user scrolls down the page and fade in when they get back to the top of the page.
The problem
This code does work but not all the time. Sometimes it will display correctly other times it won't. By that I mean the height of div.banner can be greater than the height of the browser window yet .title and .social will not be appended to the body. Is there anything wrong with this code that could cause this issue to occur?
$(document).ready(function () {
// fade in/fade out banner titles
$(window).trigger('scroll');
var divs = $('.social, div.banner .title');
$(window).scroll(function(){
if($(window).scrollTop() < 10){
divs.fadeIn("fast");
} else {
divs.fadeOut("fast");
}
});
// Position feature image title and social icons according to browser window height
var windowHeight = $(window).height(); // Gets browser viewport height
var bannerHeight = $(".banner").height(); // Gets .banner height
if (bannerHeight > windowHeight) {
$("body").append($('.banner .title'));
$("body").append($('.social'));
}
else {
//Display .title and .social in .banner div (as originally in HTML)
}
});
My HTML code that is on page load for reference:
<div class="banner y1">
<div class="title" id="feature-title">
<!-- title content here -->
</div>
<div class="social" id="feature-social">
<!-- social content here -->
</div>
</div>

If height changes on images you should use onload method.
http://api.jquery.com/load-event/