Develop Reference

Javscript detect the state of a div so I can toggle between 2 functions? (without jQuery)

I have a sidebar and I have 2 functions.
One opens it and the other one closes it.
Here are the two functions.
function openNav() {
document.getElementById("myNav").style.width = "100%";
}
function closeNav() {
document.getElementById("myNav").style.width = "0%";
}
I want to create a condition between both so I can toggle them but for that I need to detect if it's opened or closed.
How can I detect it so I can create a toggle function calling the functions above?

You don't need two functions. You can do this with just one CSS class and one function that toggles that one class on the sidebar element.
To do this, add the default width of 0% on the sidebar and then create another class, lets call it .sidebarToggle, that changes the width to 100%.
In javascript, you just need one function, lets call it toggleSidebar() that just toggles the .sidebarToggle class. This way, you not only need less code but also don't need to worry about checking whether the sidebar is opened or closed.
A Better Solution
A better approach is to change the transform property of the sidebar instead of the width. Changing transform property, in this case, is better as compared to changing width, because if you change the width, you will have to handle the:
resizing of the child elements of the sidebar as the sidebar's width is increased or decreased.
remove the left or right padding (if there's any) on the sidebar when the width of the sidebar is 0px or 0%. If you don't remove the padding, sidebar will not completely hide on 0px or 0% width.
With transform, you don't need to worry about the above mentioned points because, instead of resizing, we just translate the sidebar from one point to another.
Animating transform property is also more efficient as compared to animating the width property because changing transform property doesn't causes the browser to go through Layout and Paint steps of its critical rendering path whereas changing the width property will cause the browser to again go through these steps.
Following code snippet shows an example:
const btn = document.querySelector('button');
const sidebar = document.querySelector('.sidebar');
btn.addEventListener('click', () => {
sidebar.classList.toggle('sidebarToggle');
});
body {
margin: 0;
}
.sidebar {
display: flex;
flex-direction: column;
background: #666;
color: #fff;
padding: 15px 25px;
box-sizing: border-box;
width: 30%;
height: 100vh;
transform: translateX(-100%);
position: absolute;
transition: transform 0.5s ease;
}
span {
margin: 5px 0;
}
.sidebarToggle {
transform: translateX(0);
}
button {
position: absolute;
right: 0;
background: green;
color: #fff;
padding: 15px 25px;
}
<div class="sidebar">
<span>Item 1</span>
<span>Item 2</span>
<span>Item 3</span>
<span>Item 4</span>
</div>
<button>Toggle Sidebar</button>

This is best done with classes. That way, stying is better separated from behaviour and there is even a toggle function built in:
document.getElementById("button").onclick = function() {
document.getElementById("myNav").classList.toggle("width100");
};
#myNav {
background-color: red;
display: block;
height: 100px;
width: 0%;
}
#myNav.width100 {
width: 100%;
}
<nav id="myNav"></nav>
<button id="button">Toggle</button>

Navigation transition

I am new to jQuery and am teaching myself as I go but am struggling to figure out how to indicate that on up scroll the white navigation background moves up to show the white navigation text on panel 1?
bartaile.com is what I am using as inspiration & the changes I'm making to bartaile's navigation are---> after the user scrolls past the first panel the navigation hides, only when the user scrolls up does the navigation show again, when panel 1 comes back down the white navigation backgrouns slide up to hide and shows white text.
Any help or tips to learn how to do this would be greatly appreciated! :-)
var lastScrollTop = 0;
$(window).on('scroll', function() {
var header = $('.header');
var stage0 = $('.stage-0');
var scrollTop = $(window).scrollTop();
if (scrollTop > lastScrollTop) {
// down scroll
if (scrollTop > stage0.offset().top + stage0.height()) {
header.addClass('hide');
}
} else {
// up scroll
if (scrollTop <= stage0.offset().top + stage0.height()) {
header.removeClass('headerBGchange headerLIchange');
} else {
header.removeClass('hide').addClass('headerBGchange headerLIchange BGupTranistion');
}
}
lastScrollTop = scrollTop;
});
.header {
display: -webkit-box;
display: -webkit-flex;
display: -ms-flexbox;
display: flex;
-webkit-box-align: center;
-webkit-align-items: center;
-ms-flex-align: center;
align-items: center;
height: 80px;
-webkit-transition: top .5s ease;
transition: top .5s ease;
position: fixed;
width: 100%;
top: 0;
background-color: transparent;
overflow: hidden;
}
.header ul {
margin: 20px;
padding: 0;
}
.header ul li {
display: inline-block;
margin-right: 20px;
color: white;
}
.header ul li:last-child {
margin-right: 0;
}
.hide {
top: -80px;
}
.headerBGchange {
Background: white;
}
.BGupTranistion {
}
.header.headerLIchange ul li {
color: Blue;
}
.header.headerLIchange {
border-bottom: 1px solid black;
}'
</style>
<!--stage style--><style>
.stage {
color: #fff;
display: -webkit-box;
display: -webkit-flex;
display: -ms-flexbox;
display: flex;
-webkit-box-pack: center;
-webkit-justify-content: center;
-ms-flex-pack: center;
justify-content: center;
-webkit-box-align: center;
-webkit-align-items: center;
-ms-flex-align: center;
align-items: center;
height: 100vh;
background-color: white;
border-bottom: 1px solid black;
font-size: 48px;
height: 200px;
width: 100%;
}
.stage-0 {
background: grey;
}
.stage-24 {
background: #433937;
}
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<div class="header">
<ul>
<li>Home</li>
<li>About</li>
<li>Contact</li>
</ul>
</div>
<div class="stage stage-0">1</div>
<div class="stage stage-2">3</div>
<div class="stage stage-4">5</div>
<div class="stage stage-6">7</div>
<div class="stage stage-8">9</div>
<div class="stage stage-10">11</div>
<div class="stage stage-12">13</div>
<div class="stage stage-14">15</div>
<div class="stage stage-16">17</div>
<div class="stage stage-18">19</div>
<div class="stage stage-20">21</div>
<div class="stage stage-22">23</div>

You will need to add another container to achieve the effect you're looking for. What you essentially want to have is a container at the top and another container which will fade in and out depending on your scroll behaviour. So how do you achieve that? Create a -Element on top of the page, like your gray box is there at the moment. When scrolling down, do not transform it, instead, fade in another previously hidden container to act as your navigation when not at the top of the page. Now if you scroll back up, check the scroll location, and if the two locations of both containers overlap, start fading out the container you use when not at the top of the page. I do not think there is another solution. I might try and write a codepen on it now, I will edit my post if I had success. You could also try working it out with another div inside the actual header and z-index, though that might turn out really bad.
I have done my best to achieve what you want. Here is the CodePen.
I used two different divs, one called .dynamic-header and one normal header, and I've added a function to detect jQuery In-Viewport.
$.fn.isOnScreen = function(){
var element = this.get(0);
var bounds = element.getBoundingClientRect();
return bounds.top < window.innerHeight && bounds.bottom > 0;
}
I hope this fits your needs. Also, I changed some CSS around, using the Top-Property for the transition. You can outsource all of that into CSS classes and use them instead, but I thought this was the simplest solution for demonstration purposes. Is this what you want?
Edit 1: You named bartaile.com as an example. I took a look at the effect they create and recreated it. What you have to do is basically create a structure like this:
<div class="header-bg"></div>
<div class="header-content">
<ul>
<li>YOUR HEADER</li>
</ul>
</div>
I made another CodePen for this.
The header-bg has a height of 0. The header-content has a height of, lets say, 80px, and a background-color of transparent. Now do NOT check which direction is scrolled. The only important aspect for the effect is, how far are you from the top / is a specific element in viewport? I went for 400px from top. Now when that requirement is met, just fade in the header-bg. It will be inbetween the wrapper and the content, and will provide a background. Together with that, you may also change the color of the header-content, but I did not do that. It is what bartaile.com does, tho, so you might want to include it. Enjoy!
Edit 2: I've edited the CodePen according to your comment. See it in action here. This does the following: A header is there. When scrolling down, it'll disappear. On scroll up, it'll bring up a background, but when scrolling so that scrollTop < 400, the background will fade out. As of what I understood, this is what you want. It uses the structure I posted above.

I check out "bartaile.com" and I have to point out that what they use is a third party lib called 'fullpage'.If you wanna achieve that kind of effect, you should check out this lib fullpage.js. This is a simple and easy to use plugin to create fullscreen scrolling websites (also known as single page websites or onepage sites). It allows the creation of fullscreen scrolling websites, as well as adding some landscape sliders inside the sections of the site.
This plugin can handle "full screen scrolling" and also normal scrolling. You can achieve your effect with this much more easier

Stack of slides continuously growing

Let us say I want to design a website with four slides. I would like each slide to cover the previous one while the visitor is scrolling. Following is an attempt with stellar.js (a jquery plugin): http://jsfiddle.net/8mxugjqe/. You can see that it works for the first slide, which gets covered by the second one, but I could not have it work for the others.
HTML:
<body>
<div id="one" data-stellar-ratio=".2">
<p>This is the first div.</p>
</div>
<div id="two" data-stellar-ratio="1">
<p>This is the second one.</p>
</div>
<div id="three">
<p>Third one!</p>
</div>
<div id="four">
<p>Fourth and last.</p>
</div>
</body>
CSS:
* {
margin: 0;
padding: 0;
}
#one, #two, #three, #four {
position: absolute;
height: 100%;
width: 100%;
font-size: 5em;
}
p {
margin: 1em;
width: 60%;
}
#one {
background: red;
}
#two {
background: blue;
top: 100%;
}
#three {
background: green;
top: 200%;
}
#four {
background: yellow;
top: 300%;
}

I was able to throw something together using just jQuery and no other libraries. It relies on relative positioning. Basically, everything scrolls normally until one of the slides reaches the top of the browser window. Once it tries to scroll past the top of the browser window, I add an offset to the slide's vertical position to keep it from moving up any further. When scrolling back the other way, I simply subtract from this offset until it hits 0 at which point it begins to scroll normally again.
I'm sure the code can be cleaned up but I added a ton of comments so hopefully it's readable. If you have any questions or you would like me to modify it to better suit your needs, let me know. Here's a fiddle with the solution I came up with:
http://jsfiddle.net/jwnace/jhxfe2gg/
You can also see a full page demo of the same code here:
http://joenace.com/slides/

Position badge over corner of image automatically

I have a layout where images "float" within a certain area. The layout looks like this:
The source like this:
<div class="free_tile">
<a class="img_container canonical" href="/photos/10">
<img class="canonical" src="http://s3.amazonaws.com/t4e-development/photos/1/10/andrew_burleson_10_tile.jpg?1303238025" alt="Andrew_burleson_10_tile">
<!-- EDIT: I am aware that I can put the badge here. See the edit notes and image below. -->
</a>
<div class="location">Houston</div>
<div class="taxonomy"> T6 | Conduit | Infrastructure </div>
</div>
The CSS looks like this (in SCSS):
div.free_tile { width: 176px; height: 206px; float: left; margin: 0 20px 20px 0; position: relative;
&.last { margin: 0 0 20px 0; }
a.img_container { display: block; width: 176px; height: 158px; text-align: center; line-height: 156px; margin-bottom: 10px; }
img { margin: 0; border: 1px solid $dark3; display: inline-block; vertical-align: middle; #include boxShadow;
&.canonical { border: 1px solid $transect; }
}
.location, .taxonomy { width: 176px; }
.location { font-weight: 700; }
.taxonomy { line-height: 10px; font-size: 10px; text-transform: uppercase; height: 20px; overflow: hidden; }
}
div.transect_badge { height: 20px; width: 20px; background: url('/images/transect-badge.png'); }
So, basically the images are sitting vertically-aligned middle and text-aligned center, and they have a maximum width of 176 and max height of 158, but they're cropped to maintain the original aspect ratio so the actual top corner of each image falls differently depending on which image it is.
I have a badge that I'd like to put in the top corner of certain images (when the image is "canonical"). You see the style for this above (div.transect_badge).
The problem, of course, is I don't know where the top corner of the image will be so I can't hardcode the position via CSS.
I assume that I'll need to do this via jQuery or something. So, I started with a jQuery method to automatically append the badge div to any canonical images. That works fine, but I can't figure out how to position it over the top left corner.
How can this be done? (ideally using just HTML and CSS, but realistically using JS/jQuery)
--EDIT--
Here's the problem: The image is floating inside a container, so the corner of the image might fall anywhere inside the outer limits of the container. Here's an example of what happens if I try to use position:absolute; top:0; left:0 inside the same container the image is bound by:

It took some tryouts, but here it is: the size independent image badge positioner.
HTML:
<div class="tile">
<span class="photo">
<img src="/photos/10.jpg" alt="10" /><ins></ins>
</span>
<p class="location">Houston</p>
<p class="taxonomy">T6 | Conduit | Infrastructure</p>
</div>
CSS:
.tile {
float: left;
width: 176px;
height: 206px;
margin: 0 20px 20px 0;
}
.photo {
display: block;
width: 176px;
height: 158px;
text-align: center;
line-height: 158px;
margin-bottom: 10px;
}
a {
display: inline-block;
position: relative;
line-height: 0;
}
img {
border: none;
vertical-align: middle;
}
ins {
background: url('/images/badge.png') no-repeat 0 0;
position: absolute;
left: 0;
top: 0;
width: 20px;
height: 20px;
}
Example:
In previous less successful attempts (see edit history), the problem was getting the image vertically centered ánd to get its parent the same size (in order to position the badge in the top-left of that parent). As inline element that parent doesn't care about the height of its contents and thus remains to small, but as block element it stretches to hís parent's size and thus got to high, see demonstration fiddle. The trick seems to be to give that parent a very small line-height (e.g. 0) and display it as an inline-block. That way the parent will grow according to its childs.
Tested in Opera 11, Chrome 11, IE8, IE9, FF4 and Safari 5 with all DTD's. IE7 fails, but a center-top alignment of the photo with badge at the right position isn't that bad at all. Works also for IE7 now because I deleted the spaces in the markup within the a tag. Haha, how weird!

EDIT3: This solution is very similar to my original solution. I didn't really look at your code much so I should have noticed this earlier. Your a tag is already wrapping each image so you can just add the badge in there and position it absolute. The a tag doesn't need width/height. Also you must add the badge image at the beginning of your a tag.
Demo: http://jsfiddle.net/wdm954/czxj2/1/
div.free_tile {
width: 176px;
height: 206px;
float: left;
}
a.img_container {
display: block;
margin-bottom: 10px;
}
span.transect_badge {
display:block;
position: absolute;
height: 20px;
width: 20px;
background-image: url('/images/transect-badge.png');
}
HTML...
<a class="img_container canonical" href="/photos/10">
<span class="transect_badge"></span>
<img class="canonical" src="path/to/img" />
</a>
Other solutions...
In my code I'm using SPAN tags so simulate images, but it's the same idea. The badge image, when positioned absolute, will create the desired effect.
Demo: http://jsfiddle.net/wdm954/62faE/
EDIT: In the case that you need jQuery to position. This should work (where .box is your container and .corner is the badge image)...
$('.box').each(function() {
$(this).find('.corner')
.css('margin-top', ( $(this).width() - $(this).find('.img').width() ) / 2);
$(this).find('.corner')
.css('margin-left', ( $(this).height() - $(this).find('.img').height() ) / 2);
});
EDIT2: Another solution would be to wrap each image with a new container. You would have to move the code that you use to center each image to the class of the new wrapping container.
Demo: http://jsfiddle.net/wdm954/62faE/1/
$('.img').wrap('<span class="imgwrap" />');
$('.imgwrap').prepend('<span class="badge" />');
Technically you can just add something like this to your HTML though without using jQuery to insert it.

Use an element other than <div>, e.g. <span> and put it inside your <a> element after the <img> element. Then, give the <a> element position:relative; and the <span> gets position:absolute; top:0px; left:0px;. That is, if you don't mind the badge also being part of the same link - but it's the easiest way. Also, the reason for using <span> is to keep your HTML4 valid, <div> would still be HTML5 valid, however.

I did find one solution using jQuery. I don't prefer this because it noticably impacts page loading, but it is acceptable if nothing else will work. I'm more interested in NGLN's idea which seems promising but I haven't entirely figured out yet. However, since this thread has picked up a lot of traffic I thought I'd post one solution that I came up with for future readers to consider:
Given this markup:
<div class="free_tile">
<a class="img_container canonical" href="/photos/10">
<img class="canonical" src="http://s3.amazonaws.com/t4e-development/photos/1/10/andrew_burleson_10_tile.jpg?1303238025" alt="Andrew_burleson_10_tile">
<span class="transect-badge"></span>
</a>
<div class="location">Houston</div>
<div class="taxonomy"> T6 | Conduit | Infrastructure </div>
</div>
Same CSS as in question except:
span.transect-badge { display: block; height: 20px; width: 20px; position: absolute; background: url('/images/transect-badge.png'); }
Then this jQuery solves the problem:
$(function() {
$('img.canonical').load( function() {
var position = $(this).position();
$(this).next().css({ 'top': position.top+1, 'left': position.left+1 });
});
});
Like I said, though, this incurs noticeable run-time on the client end, so I'd prefer to use a non JS solution if I can. I'll continue to leave this question open while I test out and give feedback on the other solutions offered, with hopes of finding one of them workable without JS.

CSS or JavaScript to highlight certain area of image opacity

I'm looking to do something like this but with CSS or JavaScript.
I need to highlight a certain part of an image but everything I find is how to do it in Photoshop. Can I do this with CSS or maybe JavaScript?
Am I even asking the right question?
EDIT:
Well here is a great submission but I have a follow up question:
I need this for a mobile device and portrait and landscape views as well for many devices like: iOS, iPad, Android, WebOS, Etc... So the fixed position I'm not sure will work.
Any advice?

You could use background-position with absolutely positioned divs as follows:
CSS:
.container {
position:relative;
height:455px;
width:606px;
}
.container div {
position:absolute;
background-image:url(http://www.beachphotos.cn/wp-content/uploads/2010/07/indoensianbeach.jpg);
}
.container .bg-image {
opacity:0.3;
height:455px;
width:606px;
}
.container div.highlight-region {
height:50px;
width:50px;
opacity:0;
}
.container div.highlight-region:hover {
opacity:1;
}
HTML:
<div class="container">
<div class="bg-image"></div>
<div class="highlight-region" style="top:50px;left:50px;background-position: -50px -50px;"></div>
<div class="highlight-region" style="top:150px;left:150px;background-position: -150px -150px;"></div>
</div>
Please see http://jsfiddle.net/MT4T7/ for an example
Credit to beachphotos.com for using their image.
EDIT (response to OP comment): Please also see http://jsfiddle.net/zLazD/ I turned off the hover aspect. also added some borders.
CSS changes:
.container div.highlight-region {
height:50px;
width:50px;
border: 3px solid white;
}
/* removed :hover section */

You can probably fake it, here is a sample:
http://jsfiddle.net/erick/JMBFS/3/
I covered the image with an opaque element. The color of the element is the same as the background of the image. Used z-index to put it on top.

You sure can. For example, most crop plugins provide "highlighting" as the basis of their UI. So for a complete cross-browser solution, just use an existing plugin, like Jcrop.
Of course, you might want it to be fixed, in which case you can programmatically tell the plugin which section to highlight and that the user shouldn't be able to move it, and then it will act as a highlighter, not a cropper.

These are the steps you can take to highlight a part of an image:
Access the image in JavaScript, and dynamically add another identical image immediately after it. (this could be done just in HTML, but it would change the semantics of your markup)
Position the second image over the first image
Apply a css mask on the second image so that only the "highlighted" part shows up
When the user hovers over the images' container, adjust the opacity of the first image.
I can provide more technical details on this later if need be.

What about overlaying the cropped image (with 100% opacity) on top of the whole image (with 30% opacity)?
This answer is only a proof of concept
body {
margin: 0 0 0 0;
padding: 0 0 0 0;
}
.img {
position: absolute;
top: 0;
left: 0;
}
.img-base {
opacity: 0.3;
z-index: -99;
}
.img-overlay {
opacity: 1.0;
}
.cropper{
width: 150px; /* input width and height of the box here */
height: 120px;
overflow: hidden;
position: relative;
padding: 0 0 0 0;
margin: 0 0 0 0;
left: 90px; top: 170px; /* input starting location of the box here */
}
#overlay1 {
position: absolute;
left: 0px; right: 0px;
margin-left: -90px; margin-top: -170px; /* input starting location of the box here */
}
<img src="https://images.unsplash.com/photo-1583355862089-81e9e6e50f7a?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=334&q=80" class="img img-base">
<div class="cropper">
<img src="https://images.unsplash.com/photo-1583355862089-81e9e6e50f7a?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=334&q=80" class="img img-overlay" id="overlay1">
</div>