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.

How to set width and height of canvas to all height and width of browser without overflow?

I want to make a canvas with width and height of document without scrolls, but I don't know how to do this. I tried:
canvas.width = window.innerWidth;
canvas.width = parseInt(getComputedStyle( document.body ).getPropertyValue( 'width' ));
canvas.width = document.body.offsetWidth
canvas.width = document.body.clientWidth
But I got 1-20 unused pixels that I can scroll, also I can't reduce width and height by fixed number of pixels - different browsers show it differently.

Fixed by "display: block", canvas elements aren't blocks by default.

if you're asking how to make an element 100% of the viewport's width and height, you can use CSS...
#selector_id {
width: 100vw,
height: 100vh
}

window.innerWidth gives you the whole width inside the window frame ignoring the scroll bars.
document.body.clientWidth gives you the width inside the vertical scroll bar - if present.
These both work on current versions of Safari and Chrome - I just gave them a quick try.
Both should work on all modern browsers check here for
window.innerWidth and here for document.body.clientWidth.
I'd be interested to know any circumstances where these don't work as advertised.
(Of course if you executed the code exactly as you've shown it you would end up with just the value of document.body.clientWidth. I'm guessing you meant you tried each of them in turn.)

Calculating a responsive header's height and using the result in the style of another div's height

Please bear with me as I attempt to explain the issue I'm having. It's kinda tricky!
I have a fixed header that includes a responsive image, because of this, the height of the header depends on the width of the device. I also have a fixed footer sitting on the bottom of the screen. In-between the header and footer I have a fixed div with scrollable overflow positioned towards the left side of the screen. I need the fixed div in-between the header and footer to have a HEIGHT that is the following:
calc(100% - the header's height in px - the footer's height in px)
To do this, I know I need to use Javascript or jQuery, but I'm unsure how to go about setting that up. Furthermore, I need that styling to only be applied on a specific media query.
I have similar code that adds padding to the top and bottom of another div that is centered between the header and footer. This is the code that I'm using and it works perfectly (in the fiddle I've provided at the bottom, I don't use "DOMContentLoaded" because it doesn't quite work with JSFiddle like it should. same idea slightly different syntax in the fiddle) :
document.addEventListener("DOMContentLoaded", function() {
var headerHeight = document.getElementById('header').clientHeight;
document.getElementById("content").style.paddingTop = headerHeight + "px";
var footerHeight = document.getElementById('footer').clientHeight;
document.getElementById("content").style.paddingBottom = footerHeight + "px";
}, true);
window.addEventListener('resize', function() {
var headerHeight = document.getElementById('header').clientHeight;
document.getElementById("content").style.paddingTop = headerHeight+ "px";
var footerHeight = document.getElementById('footer').clientHeight;
document.getElementById("content").style.paddingBottom = footerHeight + "px";
}, true);
I need to use code similar to that, but instead of styling the div "content", I need to be styling a div titled "description" and instead of styling the padding, I need to be styling the height. The last difference is that the styling should only be applied to this media query:
#media screen and (orientation: landscape)
I've created a JSFiddle: http://jsfiddle.net/yg7mjhvn/
Thank you guys so much! I really appreciate it.

If I get it correctly, you just need to set the height of content/description div calc(100% - <header-height> - <footer-height>) with javascript.
So, to do that add a function setDescriptionHeight to your js code which sets the height of description div and add it as a load and resize event handler. All this will be done like this.
function setContentHeight() {
if (window.innerWidth > window.innerHeight) { // window.orientation === 90 for checking the real orientation
var headerHeight = document.getElementById('header').clientHeight;
var footerHeight = document.getElementById('footer').clientHeight;
document.getElementById("description").style.height = `calc(100% - ${headerHeight}px - ${footerHeight}px)`;
} else{
document.getElementById("description").style.height = "";
}
document.getElementById("description").style.top = `${headerHeight}px`;
}
window.addEventListener('load', setContentHeight, true);
window.addEventListener('resize', setContentHeight, true);
Now, you see that it has a condition window.orientation === 90. That is there to check whether the device is in landscape orientation, and if it is then the styling is done.
note that window.innerHeight < window.innerWidth simply detects whether the width is greater than the height. And, window.orientation === 90 checks the device orientation and it won't be 90 for a laptop or a dekstop screen. Moreover, it is deprecated now and you can see more about it here

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);

How to Center a Wrapper Div and Compensate for Scroll Bar? [duplicate]

This question already has answers here:
Prevent a centered layout from shifting its position when scrollbar appears
(7 answers)
Closed 5 years ago.
I'm not finding any real answers. Forcing the scroll bar to always be there is not an acceptable solution, IMO. When you center your wrapper div and auto set the margins how do you compensate for when the scroll bar appears?
Thanks

You need to compare the viewport height to the document height. If viewport < document then the scrollbar is visible and you need to adjust you centralising code to allow for the ~20px scrollbar.
var viewportHeight = $(window).height();
var documentHeight = $(document).height();
if (viewportHeight < documentHeight ) {
alert("Vertical scrollbar visible");
// adjust container centralisation to account for scrollbar
}
else {
alert("Vertical scrollbar not visible");
}
You will need to put this into a function which is called on $(window).resize(fn); so that it updates should the browser window be resized.
Example fiddle