We Keep Coding

Convert vh units to px in JS

Unfortunately 100vh is not always the same as 100% browser height as can be shown in the following example.
html,
body {
height: 100%;
}
body {
overflow: scroll;
}
.vh {
background-color: blue;
float: left;
height: 50vh;
width: 100px;
}
.pc {
background-color: green;
float: left;
height: 50%;
width: 100px;
}
<div class="vh"></div>
<div class="pc"></div>
The issue is more pronounced on iPhone 6+ with how the upper location bar and lower navigation bar expand and contract on scroll, but are not included in the calculation for 100vh.
The actual value of 100% height can be acquired by using window.innerHeight in JS.
Is there a convenient way to calculate the current conversion of 100vh to pixels in JS?
I'm trying to avoid needing to generate dummy elements with inline styles just to calculate 100vh.
For purposes of this question, assume a hostile environment where max-width or max-height may be producing incorrect values, and there isn't an existing element with 100vh anywhere on the page. Basically, assume that anything that can go wrong has with the exception of native browser functions, which are guaranteed to be clean.
The best I've come up with so far is:
function vh() {
var div,
h;
div = document.createElement('div');
div.style.height = '100vh';
div.style.maxHeight = 'none';
div.style.boxSizing = 'content-box';
document.body.appendChild(div);
h = div.clientHeight;
document.body.removeChild(div);
return h;
}
but it seems far too verbose for calculating the current value for 100vh, and I'm not sure if there are other issues with it.

How about:
function viewportToPixels(value) {
var parts = value.match(/([0-9\.]+)(vh|vw)/)
var q = Number(parts[1])
var side = window[['innerHeight', 'innerWidth'][['vh', 'vw'].indexOf(parts[2])]]
return side * (q/100)
}
Usage:
viewportToPixels('100vh') // window.innerHeight
viewportToPixels('50vw') // window.innerWidth / 2

The difference comes from the scrollbar scrollbar.
You'll need to add the height of the scrollbar to the window.innerHeight. There doesn't seem to be a super solid way of doing this, per this other question:
Getting scroll bar width using JavaScript

make div 100% of browser height depending on length of content

I have 2 divs, a navigation and a main content in a bootstrap grid system. The length of either can vary depending on amount of content. I need them both styled to fill 100% of the browser window IF neither has the content to reach the bottom naturally. But if at least one of the divs has more content than the length of the browser window, I need to be able to scroll down the page with the styles of both divs remaining in tact and both have a height of the longer of the 2 divs.
I'm currently using a javascript resize function which seems to work but not in the case where neither div is long enough to fill the height of the browser window. Any suggestions?
HTML
<div class="row">
<div id="nav" class="col-xs-2">
Variable Height Navigation
</div>
<div id="main" class="col-xs-10">
Variable Height Content
</div>
</div>
Javascript
function resize() {
var h = (document.height !== undefined) ? document.height : document.body.offsetHeight;
document.getElementById("nav").style.height = h + "px";
}
resize();
window.onresize = function () {
resize();
};

I am trying to understand you question, and if I'm correct what you are looking for is:
Both divs need to be equally high
They need be at least the height of the screen
They need to take the height of the highest div
So let's try to achieve this goal as simply as possible:
var main = document.getElementById('main');
var nav = document.getElementById('nav');
function resize(){
var highest;
// Set the divs back to autosize, so we can measure their content height correctly.
main.style.height = 'auto';
nav.style.height = 'auto';
// Find the highest div and store its height.
highest = main.clientHeight > nav.clientHeight
? main.clientHeight
: nav.clientHeight;
// Check if the highest value is the div or the window.
highest = highest > window.innerHeight
? highest
: window.innerHeight;
// Assign the newly found value
main.style.height = highest + 'px';
nav.style.height = highest + 'px';
}
resize();
// Also, you don't need to wrap it in a function.
window.resize = resize;
// However, better would be:
window.addEventListener('resize', resize, false);
#main, #nav {
width: 100%;
height: auto;
}
#main { background: red; }
#nav { background: green; }
<div id="main"></div>
<div id="nav"></div>
Now, If you aren't bothered with the actual sameness in heiught of both divs but just want them to at least be one screenful, you should consider using CSS:
html, body { height: 100%; }
#nav, #main { min-height: 100%; }
I think that is the better solution (no Javascript!) and sort-of does what you want, bar the fact that you won't have to equally high div elements. However, you would barely notice it as each will at least fill the page.

You could try using viewport height:
For example:
#nav {
min-height: 100vh;
}
#main {
min-height: 100vh;
}
See Bootply.
This will also remove the need for JavaScript.

Changing image widths after page had loaded if width is declared already? If width is undeclared, width will change but not if declared as I have

The trouble is that I need these images with generated IDs "cam_snap_XXX" to become a different width if they are dragged and dropped into this area. I can make the height change but NOT THE WIDTH because the width is designated to 20px if x==1. Never is the image height specified therefore I believe that is the reason it is changeable? Q: How can I make these image widths change from 20px to 100px if "dragged"?
while (cnt <= 100) {
cam_icon=document.getElementById('cam_snap_' + cnt);
cam_icon.style.visibility = 'hidden';
if (x==1) {
cam_icon.style.width = '20px';
cam_icon.style.visibility = 'visible';
}
cnt++;
}
The height changes from the following javascript...
//js for adding class "dragged" which gives new height and width image parameters
$('.droparea td.drop').droppable({
onDrag: function (e, source) {
$(this).addClass('dragged'); //Changes height correctly not width though.
}
}
And the css..
//css for attempting to change image width and height on drop
.dragged{
height: 100px; //Works because height stretches image height from ~20px to 100px.
width: 100px; //**Doesn't work and is useless because width remains 20px.**
}
Should I try removing the class before adding class 'dragged' to these images? Using removeClass()? Any ideas are welcome even if not the solution.

This part of javascript modifies your HTML
cam_icon.style.width = '20px';
cam_icon.style.visibility = 'visible';
to
<someTag id="cam_snap_x" style="width:20px;visibility:visible">
According to css rules inline style (inside an HTML element) has the highest priority. so you'll have to change attribute value to see changes in UI.
Solution 1: change your onDrag function like below.
$('.droparea td.drop').droppable({
onDrag: function (e, source) {
$(this).width(100).height(100); //This will change the style property
}
}
Solution 2: Use !important to prioritize value specified in class over inline style attribute
.dragged{
height: 100px;
width: 100px !important;
}

How do you reduce the scrollable height of a div with scaled content?

I have a scrollable div that I zoom/scale the content of using css3 transform. It works fine if I'm zooming in (scaling up the content) but I've noticed that when scaling down, below 100%, the amount that you can scroll vertically of the container div does not reduce.
I've made a jsfiddle to illustrate this
CSS:
.scrollable
{
height: 250px;
width: 250px;
overflow: auto;
background-color: green;
}
.content
{
height :500px;
width : 500px;
background: linear-gradient(red, blue);
...
}
JS/jquery:
function scaleContent(newScale){
var $content = $("#content");
var scaleString = "scale("+newScale+")";
//var height = (newScale<1)? $("#content").height()/scale*newScale : originalHeight;
$content.css({
'-webkit-transform' : scaleString,
'-webkit-transform-origin' : '0 0',
...
//'height' : height +'px'
});
scale=newScale;
}
The actual scaling and the amount that you can scroll horizontally works perfectly, but the amount you can scroll vertically doesn't change below 100%.
Note: the amount you can scroll vertically appears to change on the first scaledown/zoomout, but this is simply because the horizontal scrollbar is removed.
I tried to manually change the height of the content, but this just messed with the content dimensions (duh). That's the commented-out height code.
The ellipses are where I've repeated things for other browsers.

I've managed to come up with one solution, though it's probably not the best. I introduced another div around the content, which I call the view wrapper. I set its overflow to "hidden" and manually set its width and height to match what the scaled content should be.
CSS:
.viewwrapper{
height :500px;
width : 500px;
overflow: hidden
}
JS:
function scaleContent(newScale){
var $content = $("#content");
var scaleString = "scale("+newScale+")";
var $viewwrapper = $("#viewwrapper");
var height = $content.height()/newScale;
var width = $content.width()/newScale;
$viewwrapper.height(height);
$viewwrapper.width(width);
$content.css({
'-webkit-transform' : scaleString,
'-webkit-transform-origin' : '0 0',
...
});
}
JS Fiddle
Update:
This won't work if you're using jQuery 3.0 or 3.1. The read behaviour of the height and width functions has changed, so they return the scaled values. To fix the above code for those versions you can just say.
function scaleContent(newScale){
var $content = $("#content");
var scaleString = "scale("+newScale+")";
var $viewwrapper = $("#viewwrapper");
$viewwrapper.height($content.height());
$viewwrapper.width($content.width());
$content.css({
'-webkit-transform' : scaleString,
'-webkit-transform-origin' : '0 0',
...
});
}
JSFiddle using jQuery 3.0
However this probably won't make it into future versions of jQuery.
Update 2:
You might see unnecessary scrollbars in Chrome when you zoom out of the content. This is down to a Chrome bug.

you're applying transformations to your #content div, but the outside div, #scrollable has also a fixed height and is not reducing. You have to apply transformations to it too.
Because if you're zooming in, the outside div adapts to the inside content, whereas if you're reducing it does not.

How to reliably get screen width WITH the scrollbar

Is there a way to reliably tell a browser's viewport width that includes the scrollbar, but not the rest of browser window)?
None of the properties listed here tell me the width of the screen INCLUDING the scrollbar (if present)

I figured out how to accurately get the viewport width WITH the scrollbar using some code from: http://andylangton.co.uk/blog/development/get-viewport-size-width-and-height-javascript
Put this inside your $(document).ready(function()
$(document).ready(function(){
$(window).on("resize", function(){
function viewport() {
var e = window, a = 'inner';
if (!('innerWidth' in window )) {
a = 'client';
e = document.documentElement || document.body;
}
return { width : e[ a+'Width' ] , height : e[ a+'Height' ] };
}
});
// Get the correct window sizes with these declarations
windowHeight = viewport().height;
windowWidth = viewport().width;
});
What it Does:
When your page is 'ready' or is resized, the function calculates the correct window height and width (including scrollbar).

I assume you want to know the viewport width with scrollbar included, because the screen it self does not have a scrollbar. In fact the Screen width and heigth will be the computer screen resolution itself, so I'm not sure what you mean with screen width with the scroll bar.
The viewport however, the area where only the page (and scroll bars) is presented to the user, meaning, no browser menus, no bookmarks or whatever, only the page rendered, is where such scroll bar may be present.
Assuming you want that, you can measure the client browser viewport size while taking into account the size of the scroll bars this way.
First don't forget to set you body tag to be 100% width and height just to make sure the measurement is accurate.
body {
width: 100%;
// if you wish to also measure the height don't forget to also set it to 100% just like this one.
}
Afterwards you can measure the width at will.
Sample
// First you forcibly request the scroll bars to be shown regardless if you they will be needed or not.
$('body').css('overflow', 'scroll');
// Viewport width with scroll bar.
var widthWithScrollBars = $(window).width();
// Now if you wish to know how many pixels the scroll bar actually has
// Set the overflow css property to forcibly hide the scroll bar.
$('body').css('overflow', 'hidden');
// Viewport width without scroll bar.
var widthNoScrollBars = $(window).width();
// Scroll bar size for this particular client browser
var scrollbarWidth = widthWithScrollBars - widthNoScrollBars;
// Set the overflow css property back to whatever value it had before running this code. (default is auto)
$('body').css('overflow', 'auto');
Hope it helps.

As long as body is 100%, document.body.scrollWidth will work.
Demo: http://jsfiddle.net/ThinkingStiff/5j3bY/
HTML:
<div id="widths"></div>
CSS:
body, html
{
margin: 0;
padding: 0;
width: 100%;
}
div
{
height: 1500px;
}
Script:
var widths = 'viewport width (body.scrollWidth): '
+ document.body.scrollWidth + '<br />'
+ 'window.innerWidth: ' + window.innerWidth + '<br />';
document.getElementById( 'widths' ).innerHTML = widths;
I put a tall div in the demo to force a scroll bar.

Currently the new vw and vh css3 properties will show full size including scrollbar.
body {
width:100vw;
height:100vh;
}
There is some discussion online if this is a bug or not.

there is nothing after scrollbar so "rest of the window" is what?
But yes one way to do it is make another wrapper div in body where everything goes and body has overflow:none; height:100%; width:100%; on it, wrapper div also also has 100% width and height. and overflow to scroll. SO NOW...the width of wrapper would be the width of viewport
See Example: http://jsfiddle.net/techsin/8fvne9fz/
html,body {
height: 100%;
overflow: hidden;
}
.wrapper {
width: 100%;
height: 100%;
overflow: auto;
}

With jQuery you can calculate the browser's scrollbar width by getting the width difference when overflow: hidden is set and overflow: scroll is set.
The difference in width will be the size of the scrollbar.
Here is a simple example that shows how you could do this.

You can get the window width with scrollbar , that way:
function scrollbar_width() {
if (jQuery('body').height() > jQuery(window).height()) {
/* Modified from: http://jdsharp.us/jQuery/minute/calculate-scrollbar-width.php */
var calculation_content = jQuery('<div style="width:50px;height:50px;overflow:hidden;position:absolute;top:-200px;left:-200px;"><div style="height:100px;"></div>');
jQuery('body').append(calculation_content);
var width_one = jQuery('div', calculation_content).innerWidth();
calculation_content.css('overflow-y', 'scroll');
var width_two = jQuery('div', calculation_content).innerWidth();
jQuery(calculation_content).remove();
return (width_one - width_two);
}
return 0;
}

Check out vw: http://dev.w3.org/csswg/css-values/#viewport-relative-lengths
body {
width: 100vw;
}
http://caniuse.com/#search=vw

This is my solution for removing the 'scrollbar shadow', because scrollWidth didn't work for me:
canvas.width = element.offsetWidth;
canvas.height = element.offsetHeight;
canvas.width = element.offsetWidth;
canvas.height = element.offsetHeight;
It's easy, but it works. Make sure to add a comment explaining why you assign the same value twice :)