Develop Reference

!important and display:none and .height() weirdness

I discovered something weird yesterday when working with a piece of JS code. I had a div that was hidden (display:none), and I was using the height of it in some calculations in JS. This was all working fine, until I added my "hidden" class (which has display:none !important).
Suddenly the height was always 0. There were no other changes than !important on the display.
After some digging I've narrowed the problem down to something I find rather weird:
#b { display:none; } /* reported height is 36 */
#c { display:none !important; } /* reported height is 0 */
I've created a very basic JSFiddle to isolate this. It also uses vanilla JS to get height, which seems to work just fine / as expected.
It seems like jQuery incorrectly reports height on invisible DIVs, and that !important behaves correctly.
Is this a bug in jQuery?

I dont think this is a bug in jQuery, jQuery sets display to block for a fraction of a second to calculate height, when you set !important even that is ovverriden, thats all.
I guess we need some more explanation
There is basically no way to get the height of an element from DOM if it doesn't have any height. So when display is none, the height is nonexistent or zero.
In jQuery if display is none, we can just set display to block for a fraction of a second to get the height, during this inline style is altered as usually done by jQuery.
<div id="something" style="display:block">/div>
And then height is taken, but at this time if you have set display:none!important in css this inline style wont work, and height calculated becomes zero.
In my personal opinion its always better not to use !important as it makes your code/presentation hard to read. Css usually has multitude of ways to override styles.
If you still want to proceed, an inline !important might override your style, and calculate the height by yourself using the jQuery show for a second technique, or just override the jQuery function to calculate height :)

Position an element at the bottom of a floating div with unknown height

I am currently trying to position an element in a way that it always is at the bottom of it's parent. What's special here is that none of the heights or widths are known. I'd like to do this without tables, if at all possible (my superior is against using those. In a very religious way).
I tried the approach of using position:relative on the parent and position:absolute; bottom:0; on the box I want to have at the bottom. This, however, causes the box to overlap with the other content of the parent div since absolute positioning causes the parent to ignore the height of the positioned element. Some JavaScript is used to align the heights of the floating divs to each other. But disabled JavaScript should not completely break the layout (as in: cause content to overlap or break the "flow" of the page).
Here's the fiddle with the exact structure of my markup: http://jsfiddle.net/vbeC2/27/
I did read the "float: bottom" question on SO, but none of the answers really adressed my problem, hence the new question.

It's not the cleanest solution, but since you were already using the maxHeight bit to calculate the sizes, I just added a second each loop to check the max-height of the bottom section, and added it, so that the relative, absolute positioning would work.
http://jsfiddle.net/robsterlini/svcGB/ or http://codepen.io/robsterlini/pen/BcDyt
EDIT When you resize your browser it won't work, but you could just add a resize event that recalculated it, and you'd need to think about creating some javascript-less fallbacks, either using modernizr, or just some simple

Please find the working demo here: JS Enabled
Modified the jquery logic to calculate the height of the maximum height of the container as shown below:
$(document).ready(function(){
//Set the height of the columns to the highest value of all columns
var maxHeight = 0;
$(".same-height").each(function(){
var k = $(this).children('.headline').innerHeight() + $(this).children('.description').innerHeight()+$(this).children('.bottom').innerHeight();
maxHeight = Math.max(maxHeight,k);
});
$(".same-height").css({"height" : maxHeight});
});
If JavaScript is disabled then you should apply different styles as shown in demo here:
JS Disabled

Here is something similar to what you want to atchive but the demo is centering the
http://css-tricks.com/centering-in-the-unknown/
You should use the same trick : using css ::after/::before pseudo classes to set your footer content in your parent div

Getting div height

Firebug tells me the computed style of my_div:
width 300px
height 453.167px
Yet when I execute console.log(mydiv.style.height), it gives me an empty string, even though console.log(mydiv) logs the correct element. I am sure the page has loaded by the time this logging code is called. I'd appreciate a solution that does not use jQuery.

Depending on the browser of choice, one of these will do:
mydiv.offsetHeight
mydiv.clientHeight
Get full height of a clipped DIV
Getting the height of a div

UPDATE:
Many browser inconsistencies have been fixed since my original answer. Now the clientHeight property of a DOM element is reliable.
var height = element.clientHeight;
The Element.clientHeight read-only property is zero for elements with no CSS or inline layout boxes, otherwise it's the inner height of an element in pixels, including padding but not the horizontal scrollbar height, border, or margin.
clientHeight can be calculated as CSS height + CSS padding - height of horizontal scrollbar (if present).
Note: This property will round the value to an integer. If you need a fractional value, use element.getBoundingClientRect().
Source: https://developer.mozilla.org/en-US/docs/Web/API/Element/clientHeight
Original answer:
If you use the jQuery JS library, you can just do this:
var computed_height = $('#my_div').height();
If you use the Prototype JS library, it's similar:
var computed_height = $('my_div').getHeight();
Using a library is often the easiest & most cross-browser way to do something. Getting computed styles with vanilla js is unreliable because the properties are different across browsers.

JavaScript - Need a way to set OuterHeight of the Element

I have an container element which is sort of a layout container for its children and based on some attributes I have to arrange children.
I need simple way to set outerHeight of an element, something like,
$(e).setOuterHeight(200);
jQuery's outerHeight does not set the height at all, indeed its a readonly method.
$(e).height(200); // this clips my element
In above method, I loose borders of input of type text.
My element's children are docked based on available space and some other criteria based on data that it holds, simple layouts like float,clear etc will not work because padding etc change dynamically based on sizes. I will finally end up using Table, even if I dont want to but have no choice, but anyway thanks for the help.
Now when element is sized to more then children then there is no problem, but sometimes container element may have lesser height then the children and that time, I need to increase the size.
function calculateSize(e){
var s = {
width: $(e).innerWidth(),
height: 0
};
var ae = new Enumerator(e.children);
while(ae.next()){
var child = ae.current();
// I have tried all alternatives
// for following lines
// child.clientHeight || child.offsetHeight
// $(child).outerHeight()
// $(child).innerHeight()
s.height += $(child).outerHeight();
}
if(s.height > $(e).height()){
$(e).height(s.height);
}
}
function layoutChildren(e){
....
/// for every child c
/// some steps before
var heightForChildren =
calculatedWithPadMarginBorder(availableHeight,c);
/// tried combinations
$(c).height(heightForChildren);
/// last statement fails for button
/// as button's padding cuts itself
/// removing padding in calculation
/// cuts other input elements !!
/// some steps after
....
}
I need some explanation of how to calculate runtime height/width including/excluding padding/margin/border etc and how to set it correctly so that I dont run into problems. I cant keep on trying all permutations combinations as I dont see a correct documentation even on jQuery website.
Fixed height calculations are fine, but this is kind of a dynamic element which resizes itself and arranges children in specific order.
Problem is there is no way to set outerHeight, when we set height/width of an element, the height/width is actually inner height/width without taking margin into consideration, while when we want to resize parent, we need outerHeight, but we cannot set back the outerHeight that easily.
My calculateSize and layoutChildren are two separate methods and two separate algorithms because parent will be resized to sum of all children's height. And then height is simply divided by no. of children stacked one above other. My calculation is perfect, but in my layoutChildren method I have "outerHeight" and "outerWidth" of element and have no idea on how to set it correctly by using jQuery or any other way.

.outerHeight( value )
version added: 1.8.0
you can use jQuery.outerHeight(value) to set the value of an element's outer height. Ex: $foo.outerHeight( 200 )

If you don't have a special requirement, a standard element by default sizes its height to match its children. If you style the to float:left or float:right its default width will then also be that to contain all its children.

Ok, this is strange but this is the Answer.
There are weird controls,
SELECT
BUTTON (INPUT[type=submit|reset|button])
WebKit Browsers
Padding and Border are considered as part of OuterWidth for all controls
Padding and Border must be added to Width as OuterWidth for all controls
Padding and Border are considered as part of InnerWidth for "weird controls"
Padding and Border must be subtracted from Width before setting the Width for all "non weird controls"
Non WebKit Browsers
Padding and Border are considered as part of OuterWidth for all non "weird controls"
Padding and Border must be added to Width as OuterWidth for all non "weird controls"
Padding and Border are considered as part of InnerWidth for all non "weird controls"
Padding and Border must be subtracted from Width before setting the Width for all "non weird controls"

I would be happy to help, but I simply do not understand your question.
In regards to the documentation of the dimensions methods of jQuery I found that http://api.jquery.com/category/css/ holds documentation on both innerWidth(), innerHeight(), outerWidth() and outerHeight().
I hope this helps, otherwise, try reading through your question, making it more obvious what you need the answer for.

Applying position:absolute to a style via jQuery fails to center div horizontally upon first page load

This is a followup to my question here. I would like to understand why applying position:absolute to the CSS of a div via jQuery fails, while applying it in a static style works. Here are two jsfiddle examples:
Works: http://jsfiddle.net/jasper/Ty6Af/2/
No worky: http://jsfiddle.net/Ty6Af/3/
Note that the only difference between the two is where I apply position:absolute. Vertical centering always works, but horizontal centering does not work when the page loads for the first time. If you manually re-size the window the div will center correctly.
All of my testing has been on Chrome under Ubuntu thus far.
Anyway, I'm just now delving into the world of web development and these are exactly the kinds of 'quirks' that I need to begin understanding.
EDIT:
#Jasper found something interesting. If you make two calls to .css(), first applying position and subsequently applying a margin, it works. I would love to understand why. Here is an example: http://jsfiddle.net/jasper/Ty6Af/5/

So the issue is with how the width of the div is calculated by the browser depending on its position.
If the div is set to position : static (by default) then it's width is 100% of it's parents width and the element is not allowed to move around the page.
If the div is set to position : relative then it's width is 100% of it's parents width but it can be moved around with left.
If the div is set to position : absolute then its width is determined by the actual content of the div, for instance if there is only a 200px wide <span> element within the div then the div will be 200px wide.
You can test these observations by changing the CSS of your jsfiddle to specify position : relative (etc...) and remove the JavaScript that makes the div position : absolute, then use your Developer Tools to inspect the element and it's calculated width.
The problem with your code is that it sets the position : absolute at the same time it sets the margin of the element by using its width/height (which are calculated differently depending on the position of the element).
If you want to set the position of the div in JavaScript then you can do something like this:
$(function() {
//notice I cached the selector so it can be used in the future as well as set the position of the div
$signuparea = $('#signuparea').css({position : 'absolute'});
$(window).resize(function() {
$signuparea.css({
'margin-top' : '-' + Math.round($signuparea.height() / 2) + 'px',
'margin-left' : '-' + Math.round($signuparea.width() / 2) + 'px',
});
}).trigger('resize');
});
Here's a jsfiddle: http://jsfiddle.net/jasper/Ty6Af/8/

I believe the problem is that when you apply your left and right in your second fiddle, you have yet to add position absolute to the div. Hence, the browser has no idea what do with the left and right values and ignores them initially.
Practically speaking in your second fiddle, you only actually add the position:absolute on the resize trigger. So before you resize your actual div has no positioning.
If you instead add the position absolute on load it works fine:http://jsfiddle.net/Ty6Af/9/
Notice that if you give it position:relative from the start (like this http://jsfiddle.net/Ty6Af/11/ ) it allready applies both the left and right value. The reason you can't actually see the effect of "left" is because it is a block element.
I hope that answers your question, I'm not quite clear on where you are stuck.

http://jsfiddle.net/Ty6Af/7/ this should work, the trigger function in jquery has bugs with chrome so you have to run the function on load too.

The problem seems to be that position:absolute; negates the current layout and requires you to position it.....
See: http://jsfiddle.net/ZHaRD/
Which Jasper explains much more eloquently than myself!