Develop Reference

Using .outerWidth() & .outerHeight() with the 'resize' event to center a child element in parent

I am attempting to write some JavaScript code that will allow me to center a child element within it's parent using padding. Then using the same function to recalculate the spacing using the 'resize' event. Before you start asking me why i am not doing this with CSS, this code is only a small part of a larger project. I have simplified the code as the rest of the code works and would only serve to confuse the subject.
Calculating the space - This is the function that caculates the amount of space to be used on either side of the child element.
($outer.outerWidth() - $inner.outerWidth()) / 2;
($outer.outerHeight() - $inner.outerHeight()) / 2;
The problem
Although i have successfully managed to get the desired results with margin. Padding is causing me problems.
It appears to be increasing the width on the outer element when resized
It does not center the child element perfectly (there appears to be an offset)
The inner element collapses on resize and becomes invisible.
I realize that there may be some fundamentals regarding padding that are causing my problems however after numerous console logs and observing the data returned i still can't put my finger on the problem. Any suggestion would be very welcome. It may turn out that this is not feasible at all.
HTML
<div id="demo" class="outer">
<div class="inner">
</div>
</div>
CSS
html {
box-sizing: border-box;
}
*, *:before, *:after {
box-sizing: inherit;
}
.outer {
width:97%;
height:400px;
border:1px solid black;
margin:20px;
}
.inner {
width:40%;
height:100px;
background-color:grey;
}
JAVASCRIPT
var $outer = $(".outer");
var $inner = $(".inner");
var getSpace = function(axis) {
if (axis.toLowerCase() == "x") {
return ($outer.outerWidth() - $inner.outerWidth()) / 2;
} else if (axis.toLowerCase() == "y") {
return ($outer.outerHeight() - $inner.outerHeight()) / 2;
}
}
var renderStyle = function(spacingType) {
var lateralSpace = getSpace("x");
var verticalSpace = getSpace("y");
var $element;
if (spacingType == "padding") {
$element = $outer;
} else if (spacingType == "margin") {
$element = $inner;
}
$.each(["top", "right", "bottom", "left"], function(index, direction) {
if (direction == "top" || direction == "bottom") {
$element.css(spacingType + "-" + direction, verticalSpace);
}
else if (direction == "right" || direction == "left") {
$element.css(spacingType + "-" + direction, lateralSpace);
}
});
};
var renderInit = function() {
$(document).ready(function() {
renderStyle("padding");
});
$(window).on("resize", function() {
renderStyle("padding");
});
}
renderInit();
EXAMPLE - link

Although I completely disagree with this approach to horizontally centring an element, hopefully this will help you on your way.
Fiddle: https://jsfiddle.net/0uxx2ujg/
JavaScript:
var outer = $('.outer'), inner = $('.inner');
function centreThatDiv(){
var requiredPadding = outer.outerWidth() / 2 - (inner.outerWidth() / 2);
console.log(requiredPadding);
outer.css('padding', '0 ' + requiredPadding + 'px').css('width','auto');
}
$(document).ready(function(){
// fire on page load
centreThatDiv();
});
$(window).resize(function(){
// fire on window resize
centreThatDiv();
});
HTML:
<div class="outer">
<div class="inner">Centre me!</div>
</div>
CSS:
.outer{ width:80%; height:300px; margin:10%; background: tomato; }
.inner{ width:60px; height:60px; background:white; }
Furthered on from why I disagree with this approach - JavaScript shouldn't be used to lay things out. Sure - it can be, if it really needs to be used; but for something as simple as centring an element, it's not necessary at all. Browsers handle resizing CSS elements themselves, so by using JS you introduce more headaches for yourself further down the line.
Here's a couple of examples of how you can achieve this in CSS only:
text-align:center & display:inline-block https://jsfiddle.net/0uxx2ujg/1/
position:absolute & left:50% https://jsfiddle.net/0uxx2ujg/2/ (this can be used for vertically centring too which is trickier than horizontal)

You can create the new CSS class to adjust for elements size on $window.onresize = function () {
//add your code
};

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.

Trying to get a div to always match the height of a div whose height is constantly increasing and decreasing

I have a div that contains a list of items. The user is able to add to/remove items from the list, so the div constantly changes height to compensate for the changing size of the list.
I have another div to its right that is supposed to give details about the items on the left. How can I get the div on the right to constantly keep vertically aligned with the left div and change height so that it equals the height that the left div currently is, as items are added and removed from the left div's list?
I tried to implement tables for this solution, but I find that it isn't working with my code, so instead I tried this JS code...
See this fiddle: http://jsfiddle.net/r6sc27ck/
The code might achieve what I want but the background on the left div isn't displaying so something's going wrong...
HTML
<div id="Div2">Hello2</div>
<br>
<div id="Div1">Hello1</div>
CSS
#Div1{
background-color:blue;
}
#Div2{
background-color:red;
}
JS
$(document).ready(function(){
document.onchange=setDivHeight();
function setDivHeight(){
var x=Number(document.getElementById('Div1').style.height)
document.getElementById('Div2').style.height=x;
}
});
setInterval(function() {
$('#Div1').eq(0).append('<p>appended content</p>')
}, 1000)
http://jsfiddle.net/r6sc27ck/

Instead of using document.onchange, you should call setDivHeight() in the end of the process that add content to the div.
I also modified the style and the content of setDivHeight().
http://jsfiddle.net/r6sc27ck/4/
var prevHeight;
$(document).ready(function(){
prevHeight = $('#Div1').height();
});
function setDivHeight(){
var curHeight = $('#Div1').height();
if (prevHeight !== curHeight) {
prevHeight = curHeight;
setDivHeight();
}
$('#Div2').height($('#Div1').height());
}
setInterval(function() {
$('#Div1').eq(0).append('<p>appended content</p>');
setDivHeight();
}, 1000)

If you have 2 divs next to eachother you can allign them by setting vertical-allign:
div{
vertical-align: top;
}
JSFiddle

You can set the two divs to display:table-cell and the containing div to display:table. Here is the updated fiddle http://jsfiddle.net/r6sc27ck/1/
Also there are many ways to achieve this, have a look here. https://css-tricks.com/fluid-width-equal-height-columns/

Try
css
#Div1 {
display:inline-block;
position:relative;
background-color:blue;
width:35%;
}
#Div2 {
display:inline-block;
position:relative;
background-color:red;
width:35%;
}
js
$(document).ready(function () {
setInterval(function () {
$("#Div1").eq(0).append("<p>appended content</p>");
$("#Div2").eq(0).append("<p> </p>");
}, 1000)
});
jsfiddle http://jsfiddle.net/vnt83hz7/4/

Resize a div according to the window scrolling and the div min height

I'm trying to achieve this:
When users scroll page, i need a header that will be fixed, but before to stick it, this div should shrink to a certain height, and after that this div become fixed.
This is my attempt
As you can see, there are some strange behavior on shrinking, i think that my approach is not so right.
header.css("height", "-=" + (Math.abs(start - scrollTop)));
spacer.css("height", "-=" + (Math.abs(start - scrollTop)));
So, what is the best way to do it?
UPDATE:
Now i'm at this point, but i need to make it more smooth
jsFiddle

Try this
$(document).ready(function(){
var headerElement = //Select header element here,
scrollTopToLookoutFor = //Put value you want to check for here,
if($("body").scrollTop() > scrollTopToLookoutFor || $("html").scrollTop() > scrollTopToLookoutFor){
headerElement.addClass("fix-header");
}
else{
headerElement.removeClass("fix-header");
}
});
Have a css class here with required styles
.fix-header{
height: 400px;
position: fixed;
top: 0px;
}

Scrollpane on the bottom, css is hacky, javascript is hard

I want to put a bar on the bottom of my page containing a varying number of pictures, which (if wider than the page) can be scrolled left and right.
The page width is varying, and I want the pane to be 100% in width.
I was trying to do a trick by letting the middle div overflow and animate it's position with jquery.animate().
Like this:
Here is a fiddle without the js: http://jsfiddle.net/SoonDead/DdPtv/7/
The problems are:
without declaring a large width to the items holder it will not overflow horizontally but vertically. Is this a good hack? (see the width: 9000px in the fiddle)
I only want to scroll the middle pane if it makes sense. For this I need to calculate the width of the overflowing items box (which should be the sum of the items' width inside), and the container of it with the overflow: hidden attribute. (this should be the width of the browser window minus the left and right buttons).
Is there a way to calculate the length of something in js without counting all of it's childrens length manually and sum it up?
Is there a way to get the width of the browser window? Is there a way to get a callback when the window is resized? I need to correct the panes position if the window suddenly widens (and the items are in a position that should not be allowed)
Since the window's width can vary I need to calculate on the fly if I can scroll left or right.
Can you help me with the javascript?
UPDATE: I have a followup question for this one: Scroll a div vertically to a desired position using jQuery Please help me solve that one too.

Use white-space:nowrap on the item container and display:inline or display:inline-block to prevent the items from wrapping and to not need to calculate or set an explicit width.
Edit:: Here's a live working demo: http://jsfiddle.net/vhvzq/2/
HTML
<div class="hscroll">
<ol>
<li>...</li>
<li>...</li>
</ol>
<button class="left"><</button>
<button class="right">></button>
</div>
CSS
.hscroll { white-space:nowrap; position:relative }
.hscroll ol { overflow:hidden; margin:0; padding:0 }
.hscroll li { list-style-type:none; display:inline-block; vertical-align:middle }
.hscroll button { position:absolute; height:100%; top:0; width:2em }
.hscroll .left { left:0 }
.hscroll .right { right:0 }
JavaScript (using jQuery)
$('.hscroll').each(function(){
var $this = $(this);
var scroller = $this.find('ol')[0];
var timer,offset=15;
function scrollLeft(){ scroller.scrollLeft -= offset; }
function scrollRight(){ scroller.scrollLeft += offset; }
function clearTimer(){ clearInterval(timer); }
$this.find('.left').click(scrollLeft).mousedown(function(){
timer = setInterval(scrollLeft,20);
}).mouseup(clearTimer);
$this.find('.right').click(scrollRight).mousedown(function(){
timer = setInterval(scrollRight,20);
}).mouseup(clearTimer);
});

Thanks Phrogz for this part -- give the image container the white-space: nowrap; and display: inline-block;.
You can calculate the width without having to calculate the width of the children every time but you will need to calculate the width of the children once.
//global variables
var currentWidth = 0;
var slideDistance = 0;
var totalSize = 0;
var dispWidth = (winWidth / 2); //this should get you the middle of the page -- see below
var spacing = 6; //padding or margins around the image element
$(Document).Ready(function() {
$("#Gallery li").each(function () {
totalSize = totalSize + parseFloat($(this).children().attr("width"));// my images are wrapped in a list so I parse each li and get it's child
});
totalSpacing = (($("#Gallery li").siblings().length - 1) * spacing); //handles the margins between pictures
currentWidth = (parseFloat($("#Gallery li.pictureSelected").children().attr("width")) + spacing);
maxLeftScroll = (dispWidth - (totalSize + totalSpacing)); //determines how far left you can scroll
});
function NextImage() {
currentWidth = currentWidth + (parseFloat($("#Gallery li.pictureSelected").next().children().attr("width")) + spacing); //gets the current width plus the width of the next image plus spacing.
slideDistance = (dispWidth - currentWidth)
$("#Gallery").animate({ left: slideDistance }, 700);
}
There is a way to get the browser window with in javascript (jQuery example).
and there is a way to catch the resize event.
var winWidth = $(window).width()
if (winWidth == null) {
winWidth = 50;
}
$(window).resize(function () {
var winNewWidth = $(window).width();
if (winWidth != winNewWidth) {
window.clearTimeout(timerID);
timerID = window.setInterval(function () { resizeWindow(false); }, 100);
}
winWidth = winNewWidth;
});
On my gallery there's actually quite a bit more but this should get you pointed in the right direction.

You need to change your #items from
#items
{
float: left;
background: yellow;
width: 9000px;
}
to
#items {
background: yellow;
}
Then calculate the width very easily with jQuery
// #items width is calculated as the number of child .item elements multiplied by their outerWidth (width+padding+border)
$("#items").width(
$(".item").length * $(".item").outerWidth()
);
and simply declare click events for the #left and #right elements
$("#left").click(function() {
$("#middle").animate({
scrollLeft: "-=50px"
}, 'fast');
});
$("#right").click(function() {
$("#middle").animate({
scrollLeft: "+=50px"
}, 'fast');
});
jsFiddle link here
EDIT
I overlooked that detail about the varying image widths. Here is the correct way to calculate the total width
var totalWidth = 0;
$(".item").each(function(index, value) {
totalWidth += $(value).outerWidth();
});
$("#items").width(totalWidth);