Develop Reference

How to know whether a browser is displaying scrollbar is present or not in reactjs?

I am working on react project. when we make the screen size decrease from large to tiny, a scroll bar is appearing in the browser and as a result my testcases are failing.I wanted to know is there any way we can find whether a scroll bar is displayed in the browser for all types of screen sizes. Also is there any way to get the size of the scroll bar being displayed in the browser?

You can compare the height of your content with the height of the window.
So if (document.body.offsetHeight > window.innerHeight) then the scrollbar would be visible.
UPD:
Regarding scrollbar's sizes. Its width is just a difference between window.innerWidth and document.body.offsetWidth, and its height is equal to window.innerHeight.
So summing up:
let scrollbarSize = {
heigth: window.innerHeight,
width: window.innerWidth - document.body.offsetWidth
}

I would have preferred a comment but I do not have access to that yet.
I am assuming you are talking about height here if not please apply the same solutionwhere appropriate.
To know whether your browser is displaying the vertical scrollbar. Compare the height of the document and the screen height.
Method for the calculation of document height would usually vary across browsers in this case. Use something like this:
let scrollHeight = Math.max(
document.body.scrollHeight, document.documentElement.scrollHeight,
document.body.offsetHeight, document.documentElement.offsetHeight,
document.body.clientHeight, document.documentElement.clientHeight
);
To calculate your window height use:
const windowHeight = documentElement.clientHeight
If your scrollHeight is greater than the windowHeight then you can be most certain that the vertical scrollbar is present.
Therefore it would be easy to detect

In this sandbox I have tested two posible solutions. First approach (ScrollableComponent and hook useIsScrollable) is based on trying to scroll with element. If it does something then you know that it has scrollbar. The second aproach is based on measuring (ScrollableComponentA and hook useIsScrollableA). Measure wrapper element and inner element and compare its height and width.

Retrieving viewport height of screen in mobile browsers with jquery

I'm attempting to get the viewport height in mobile browsers WITHOUT the height of the browser bar but all of the solutions I've attempted have come up short.
What others have suggested is using the below, however it does not work for me. I still get a blank white bar at the bottom of the window when scrolling
var screenHeight = window.innerHeight;
$('.mobile-nav-wrapper').height(screenHeight)

I believe what you are looking for is scrollHeight
The scrollHeight property returns the entire height of an element in
pixels, including padding, but not the border, scrollbar or margin.
You can try this:
document.body.scrollHeight

Solution 1:
I don't have an answer using jQuery. But using a plain/vanilla JavaScript wouldn't cause any issue :).
Following script allows you to detect the Viewport size (height and width) reliably.
https://github.com/tysonmatanich/viewportSize
Sample usage:
<script type="text/javascript">
var width = viewportSize.getWidth();
var height = viewportSize.getHeight();
</script>
I have used it in couple of projects, were i have to re-initialize some widgets based on current Viewport width/height rather than using window width/height (Window width/height calculation isn't consistent in all browsers - some include scroll bar size 16px as a part of window width and some doesn't).
Sample Test page:
http://tysonmatanich.github.io/viewportSize/
Solution 2: (Just for reference - Not an answer to OP's question, though it is related so I thought that it can remain)
Well modernizr has a very good addition Modernizr.Mq. Through which you can cross check which break point range you are in...
if(Modernizr.mq("(min-width:320px)")){
//Do job 1
}
else if (Modernizr.mq("(min-width:768px)")){
//Do job 2
}
or
based on height
Modernizr.mq("(min-height: 800px)")
http://tysonmatanich.github.io/viewportSize/

CSS / jQuery: Placing items at window height causing layout issues

Currently I am using jQuery to position a few elements relative to the size of the window. While this works perfectly if the window is full size, if I have the debugger open or a shorter window, the resulting layout is incorrect.
Q: Is there anyway to place things relative to the maximum possible window height, rather than the current window height?
jQuery
var navbarHeight = parseInt($(".navbar").css("height"));
$("#home-part-1").css("height", $(window).innerHeight() - navbarHeight);
$("#home-part-2").css("height", $(window).innerHeight());
$("#home-part-3").css("height", $(window).innerHeight());
$("#divider-1").css("top", $(window).innerHeight() - navbarHeight);
$("#divider-2").css("top", (2 * $(window).innerHeight()) - navbarHeight);

It is bad practice to try to lay out your page this way. There is not a lot I can do to help with the solution you are specifying. Its not going to work that way. Take a look at this though: http://alvarotrigo.com/fullPage/#firstPage . That might help you.

Using returned viewport queries as SASS variables

I just don't see anyone talking about this exact issue out there. Looking to have site fit any screen exactly with no scroll. Certain elements being fixed ratio (logo, video players, etc) means other areas have to expand/contract amorphically to accomodate their fixed behavior that can't ever go past 100% width or height. Difficult to explain, but the behavior in sassmeister gist below shows it working. To do this, I need to be able to define widths in terms of heights, and vice-versa (width = 56.25% of height, etc)
I can make it work using vh, vw, vmin, a bunch of calc functions etc... but browser support is patchy, and I'm unaware of a polyfill to smooth all that out. My vh, vw, calc solution below:
http://sassmeister.com/gist/3dee56a4092a86cf070a
Only other pure css I'm aware of that even begins to address this is the percent padding trick tying padded height to parent width, but this alone isn't enough. I need to be able to use min, max statements, and tie width and height going both ways.
So... unless I'm mistaken, #media queries only ever return true/false, so they can't provide an actual viewport measurement to use, right? That's what I really need... a pixel accurate measurement of the available viewport height and width.
What's the solution here? Should I use javascript to get those exact dimensions, then do all the arranging in javascript? Use JS to get the variables, then pass them on to the css?
Something like this: https://gist.github.com/scottjehl/2051999 and a method to import those returned values into css should work, no? Is that slowing the site down too much to have the js call first before anything else happens?
Also, need to find the right way to do all these calculations. Should I just be using javascript to do all the calcs and leaving stuff like the following out of css completely?
$gutter: calc(((100vh + 100vw) / 2) * 0.04)
Then using that variable inside another function:
$column-width: calc(100vw - (1.7778 * (100vh - 2 * $gutter)) - 3 * $gutter)
You get the idea. I think I'm nearing the end of what I can do with the css. JS solution? Hybrid? Something else?
thx.

It sounds like media queries are what you're looking for.
You can use the following to target screens with a max width of 1200 px and a min width of 800:
#media all and (max-width: 1200px) and (min-width: 800px) {
//some css here
}
Check out the way bootstrap-sass implements containers here.
Also check out the other SO answer about media queries.
You can even specify landscape and portrait layouts.
#media (orientation:portrait) { ... }
Or aspect ratio:
#media screen and (device-aspect-ratio: 16/9) { ... }
I hope this helps. You can use some of those fancy gutter calculations inside of/with media queries and that should simplify things a bit.
This javascript will return the screen height:
var x = "Total Height: " + screen.height;
document.getElementById("demo").innerHTML=x;
Width:
var x = "Total Width: " + screen.width;
document.getElementById("demo").innerHTML=x;
Some JQuery:
$(window).height(); // returns height of browser viewport
$(document).height(); // returns height of HTML document
$(window).width(); // returns width of browser viewport
$(document).width(); // returns width of HTML document

Calculating Height of Sidebar Dynamically

I'm trying to work out the algorithm for a fixed div that grows in height (while scrolling) until it's equal to the height of the viewport or div with fixed position relative to another div and the bottom of the viewport
I am using Twitter Bootstrap affix to lock my secondary navigation bar (yellow) and my sidebar (black) to the top of the screen when the user scrolls that far. 
This works fine. The sidebar is the piece that's giving me trouble.  When it is in its in its starting position (as shown in the diagram belorw), I want the top of the bar to sit 30px
down from the secondary navigation bar (yellow) and 30px up from the bottom of the page. 
As the user scrolls, the bar should grow in height so that it remains 30px beneath the secondary navigation bar and 30px above the bottom of the screen (As shown in the diagram below)
After the bar is fixed position, I am able to do what I need to do.  
.sidebar { 
position:fixed;
top:100px;  
bottom:30px;
left:30px;
}
What I can't figure out is how to position the TOP of the sidebar relative to my
secondary navigation bar and the BOTTOM of my sidebar relative to the bottom
of the screen. I've tried calculating the height of the sidebar at the beginning and the end of the
scroll but this causes issues.
I've also tried calculating the final height of the sidebar and letting the bottom of
the sidebar just run off the edge of the screen (when it's in its initial position), but
if there's not enough content on the right side to warrant scrolling, I have no way
of getting to the bottom items in the scroll bar.  Plus my screen starts bouncing
in a really un­attractive way.
below is the current code in use:
ShelvesSideBar.prototype._resize_sidebar = function(_this) {
var PADDING = 50;
var window_height = $(window).height(),
nav_bar_height = $('.nav_bar').height() + $('.secondary_tabs').height(),
sidebar_height = window_height - nav_bar_height - PADDING,
sidebar_scrollable_height = sidebar_height - $('.bar_top').height();
_this.$container.height(sidebar_height);
_this.$container.find('.bar_bottom').height(sidebar_scrollable_height);
/* reset the nanoscroller */
_this.$container.nanoScroller();
};
   
this code is called on page load and again on window resize. Any help would be greatly appreciated!

I've been trying to do something similar (minus the fixed elements and navbars). What I found was in order to do any sort of relative height scaling every element above the element I wished to scale all the way up to the opening html tags had to have a relative height set, even if it was just height:100%;. (here's my original question Variable height, scrollable div, contents floating)
My goal was to have the body height fixed to window size like a native full screen application would be with my content subareas scrolling, so this is a bit off topic for what you're wanting to accomplish. But I tried using JS/JQ to start off with as you're trying to do currently and found that I simply couldn't get the window height because the default behaviour for height management is to expand the page height until everything on the page fits. And all the getHeight methods I tried we're getting the page height not window/viewport height as promised. So you may wish to try fixing your body's height to the window and going from there using overflow:scroll; to scroll the page.
A quick note on overflow:scroll; if you have users who use WP8 IE (and probably other versions of IE) it may be advantageous to implement FTscroller to handle all your scroll elements as the overflow property defaults to hidden and is a fixed browser property. The only problem with FTscroller is because it uses CSS offsets to move the content container it may wreak havoc on elements that are designed to switched to fix when they reach x height from top of page because technically the top of page (or rather the top of the container they're in) isn't at the top of the page anymore it's beyond it. Just something to be aware of if you do need to cater for this browser.
And apologies for the complexity of my sentence structure. :/

so I was able to figure this out, for anyone still looking. What I ended up doing was binding to the window scroll event and - whenever the scroll occurred - I check if the class "affix" has been added to the sidebar. If it has, then I perform one set of calculations to determine sidebar height. Otherwise, I perform the other set of calculations. Code below:
/* called on window scroll */
var PADDING = 70;
var window_height = $(window).height(),
nav_bar_height = $('.nav_bar').height() + $('.secondary_tabs').height(),
header_height = $('.prof_block').height() - nav_bar_height,
sidebar_height = _this.$container.hasClass("affix") ? window_height - nav_bar_height - PADDING : window_height - (header_height + nav_bar_height) - PADDING,
sidebar_scrollable_height = sidebar_height - $('.bar_top').height();
_this.$container.height(sidebar_height);
_this.$container.find('.bar_bottom').height(sidebar_scrollable_height);