Develop Reference

Get element position relative to screen. (Or alternative solution)

I am aware this had been asked before, but no answer actually did the trick as far as I tested them.
Basically what I need is to change some element styles as soon as it "hits" the top border of the screen while scrolling down. This element is a 'Back to Top' button that will be sitting in a section and start following the user when they scroll pass said section.
I am not asking about CSS properties, I am asking about some JS property or method that allow me to know this. IE:
$('#back').distanceFromTopOfTheScreen() // This value will decrease as I scroll down
I know there are other soultions, but the client has asked for this behavior.
Any idea?

You can :
distance = $('#eleId')[0].getBoundingClientRect().top;
For more about getBoundingClientRect() look at the MDN Documentation
Note: This value change when you're scrolling, it gives you the distance between the top border of the element and the top of the Page

Sometimes JQuery make's everything more confusing than Native Javascript, even forgothing the very basics functions:
window.onscroll = function() { fixPosition()};
function fixPosition() {
var Yplus = 4; //number of lines in every scroll
document.getElementById('element').style.top = document.body.scrollTop + Yplus ;
}
This will allows you to move an "element" static on the window following the scroll.

Get vertical scroll position of next/previous waypoint

I'm using the Waypoints plugin to create some fancy navigation on scroll. So that I can force the user to scroll to the next/previous Waypoint, I'm attempting to collect the vertical scroll position of the current, active and next Waypoint:
$('.waypoint').waypoint(function(direction) {
var
currentWpId = this.element.id,
currentWpPos = $('#'+currentWpId).scrollTop(),
nextWpPost = $('#'+currentWpId).next().scrollTop(),
prevWpPost = $('#'+currentWpId).prev().scrollTop();
console.log( currentWpPos );
console.log( nextWpPost );
console.log( prevWpPost );
});
Unfortunately jQuery's scrollTop() function returns 0 for all elements. After doing some reading I believe this is a result of the elements having height: 100%; which I cannot remove due to some other CSS requirements. (Although I'm not certain this is the root cause of the issue.) Is there a way around this?
After looking for some alternative solutions, I thought to myself the Waypoints
plugin must know the values I'm trying to acquire to trigger a waypoint event! When looking at the this element, that indeed seems to be the case:
So, as an alternative, is there a way to acquire any array/object of all the Waypoint objects so I can grab these triggerPoint values?

scrollTop returns the scroll value of a scrollable element. For example, $(window).scrollTop() returns how much a user has scrolled on the page. I believe you have this confused with the element's position in the document, which you can get by calling .offset(). Offset will return a an object with top and left coordinates. In the end, you're looking for $(elem).offset().top.

Test if element can be seen by the user on an html page

Is there any way to know if an element is visible on an html page?
Like this:
One can probably do it considering the horizontal/vertical scrolling positions, the width/height of the browser window and the position/size of the element on the page, but I have little experience in jQuery so I don't know how to do it. And there might be a simple function one can call, I don't know.

You can use the .is(':visible') selectors to check if an element is currently visible in the DOM.
Edit:
However, as #BenM mentioned, this doesn't check if the elements on your page are actually out of your scrollable range - a great little plugin you could use in that case would be Viewport Selectors for jQuery.

Here is some code that I use to do this. It has been tested to work great.
function isVisible($obj) {
var top = $(window).scrollTop();
var bottom = top + $(window).height();
var objTop = $obj.offset().top;
var objBottom = objTop + $obj.height();
if(objTop < bottom && objBottom > top) {
//some part of $obj is visible on the screen.
//does not consider left/right, only vertical.
}
}

So DOM scrollIntoView aligns top/bottom, but what about left/right?

I would like to scroll horizontally the given element. The only way I find is using ScrollIntoView DOM method, which allows either align the element's bottom with the view bottom or the top - with the view top.
But what if the element is OK with respect to the Y axis, and I only want to scroll it horizontally? How can I align its left with the view left or its right with the view right?
EDIT
Here is more context. I have a YUI table with a horizontal scrollbar. I wish to scroll it programmatically to a certain TD node. I do not think window.scrollTo is of any help to me, since the scrollbar is on a div element, not on the whole page.
EDIT2
Turns out there is a duplicate SO question with the right answer - How can I scroll programmatically a div with its own scrollbars?
Voting to close mine.

I've recently had a problem with a table header that had inputs as filters for each column. Tabbing through the filters would move the focus, but if one of the inputs wasn't visible or if it was partly visible, it would only JUST bring the input into view, and I was asked to bring the full input and column into view. And then I was asked to do the same if tabbing backwards to the left.
This link helped to get me started: http://www.webdeveloper.com/forum/showthread.php?197612-scrollIntoView-horizontal
The short answer is that you want to use:
document.getElementById('myElement').scrollLeft = 50;
or:
$('#myElement')[0].scrollLeft = 50;
Here's my solution (which may be overkill for this question, but maybe it'll help someone):
// I used $.on() because the table was re-created every time the data was refreshed
// #tableWrapper is the div that limits the size of the viewable table
// don't ask me why I had to move the head head AND the body, they were in 2 different tables & divs, I didn't make the page
$('#someParentDiv').on('focus', '#tableWrapper input', function () {
var tableWidth = $('#tableWrapper')[0].offsetWidth;
var cellOffset = $(this).parent()[0].offsetLeft;
var cellWidth = $(this).parent()[0].offsetWidth;
var cellTotalOffset = cellOffset + cellWidth;
// if cell is cut off on the right
if (cellTotalOffset > tableWidth) {
var difference = cellTotalOffset - tableWidth;
$('#tableWrapper').find('.dataTables_scrollHead')[0].scrollLeft = difference;
$('#tableWrapper').find('.dataTables_scrollBody')[0].scrollLeft = difference;
}
// if cell is cut off on the left
else if ($('#tableWrapper').find('.dataTables_scrollHead')[0].scrollLeft > cellOffset) {
$('#tableWrapper').find('.dataTables_scrollHead')[0].scrollLeft = cellOffset;
$('#tableWrapper').find('.dataTables_scrollBody')[0].scrollLeft = cellOffset;
}
});

This is something I used a while back. There might be better and more efficient way of doing it but this gets the work done:
$(".item").click(function(event){
event.preventDefault();
// I broke it down into variable to make it easier to read
var tgt_full = this.href,
parts = tgt_full.split("#"),
tgt_clean = parts[1],
tgt_offset = $("#"+tgt_clean).offset(),
tgt_left = tgt_offset.left;
$('html, body').animate({scrollLeft:tgt_left}, 1000, "easeInOutExpo");
})
You just need to make sure that the item is an a tag with an href that corresponds to the target id element:
HTML:
go to section 1
...
<section id="one"> Section 1</section>
Hope this helps!

Scroll a div vertically to a desired position using jQuery

This is a followup question for this:
Scrollpane on the bottom, css is hacky, javascript is hard
I ended up doing the scrolling in the same way explained in the accepted answer.
Now there is a request that one item is selected somehow (eg. as an url parameter or by some javascript calls) I should scroll the pane to the item with the corresponding ID in the scrollpane. Like a link to an anchor () would work!
I want to make a javascript call like this
function scrollTo(id) {
$('#middle').magicallyScrollThatItemWouldBeVisible(itemid);
}
But this is not in jQuery (or at least I don't know of it). So is there a way to make it?
I'll post a simple jsFiddle here:
http://jsfiddle.net/ruisoftware/U6QdQ/4/
Help me write that scrollTo function!
A .animate would be fine too.
UPDATE: If it was not clear I would like it to only align to the left or right side of the panel, it it was overflowed on that side (so the minimum possible amount of scrolling happens)

It's not jQuery, just JavaScript, and I've actually never used it all, so I'm not sure how you would have to mess with it to get it to work in this situation, but there is a scrollIntoView function:
yourElement.scrollIntoView();

Since the elements have a fixed width, you can count the number of elements by using .index() + 1, and animate to this value (after subtracting the container's width).
If you want the element to be centered, use - Math.round(middle.width()/100)*50.
Fiddle: http://jsfiddle.net/U6QdQ/17/
//This code should be run on load / DOMReady
(function($){ //Run on load / DOMReady
$.fn.magicScrollTo = function(){
var middle = $("#middle");
var currentScrollLeft = middle.scrollLeft();
var width = middle.width();
var newScrollLeft = this.offset().left + currentScrollLeft - middle.offset().left;
if(newScrollLeft >= currentScrollLeft && newScrollLeft <= currentScrollLeft + width - this.outerWidth()) return;
if(newScrollLeft > currentScrollLeft){ //If the element is at the right side
newScrollLeft = newScrollLeft - width + this.outerWidth();
}
middle.animate({
scrollLeft: newScrollLeft,
}, 'fast')
}
})(jQuery);
Usage:
//Select the 4rd element, and scroll to it (eq is zero-based):
$('.item').eq(3).magicScrollTo();

Something along these lines would be a good start:
http://jsfiddle.net/vHjJ4/
This will bring the target into the centre of the carousel. I think you will have to add in some extra checks to make sure that it didn't scroll to far, for example if you targeted the first or last element...unless this is built into the scroll function (it might be).

I'm not sure I understand your question exactly, but it sounds like you're asking how to scroll horizontally to the selected item in the bottom pane. If so, try something like this:
//get the position of the element relative to the parent ("middle")
var pos = $("#itemid").position();
if (pos){
$("#middle").scrollLeft(pos.left);
}
From here, you can use the width of middle to center the item if needed.