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Adding and removing classes on mouse enter and leave on canvas shape

I'm trying to add a class to a element when mouse hovers over it and then remove it when mouse leaves. It works currently only with giving it direct style in js.
As shown below I tried various ways to do this, all had some problems. Only the direct style change worked. On mouse leave I do the same but remove the class. The mouse over and leave checks canvas element.
poly.on('mouseover', function () {
this.opacity(1);
layer.draw();
$('.' + this.name()).css({ backgroundColor: "#ffcc00" });
//$('.' + this.name()).classList.add("textboxhighlight");
//$('.' + this.name()).className += " textboxhighlight";
//$('.' + this.name()).addClass("textboxhighlight");
//$('.' + this.name()).setAttribute("class", "textboxhighlight");
});
I'm not sure what the problem is as I tired various methods in adding class all of them with different problems. Using just this.addClass wont work as it needs to start with $('.' + this.name()) or nothing works in the code not even forcing the style part. $('.' + this.name()) refers to a class name in element with the same name as poly.
In css:
.textboxhighlight {
background-color: #ffcc00;
}
Thanks for any help.

May be you have to use in your css class background-color: #red !important. See working example here

It would be easier if you provided more code to work with. The example below will illustrate on how to add a class on hover and remove a class on leaving the element.
$('#element').hover(function(e) {
$(this).addClass('selected');
}, function(a) {
$(this).removeClass('selected');
});
.selected {
background-color: green;
}
<div id='element'>
element
</div>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>

Hard to say what is wrong with your code when you don't show the mouseenter/leave parts of your code. But here is an example with classes:
https://codepen.io/andeersg/pen/MOGqPQ
$('.el').mouseenter(function() {
$(this).addClass('el-hover');
});
$('.el').mouseleave(function() {
$(this).removeClass('el-hover');
});

You can use toggleClass on hover event
$(".hoverclass").hover(function () {
$(this).toggleClass("hoverclass_toggle");
});
.hoverclass {
height: 72px;
width: 100%;
border: 1px solid #000;
}
.hoverclass_toggle {
background-color: #000;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="hoverclass">
<div class="item">
<div id="item1"> <i class="icon"></i>Test</div>
</div>
<div>
Otherwise you can do that type :
$(".hoverclass").hover(
function () {
$(this).addClass("result_hover");
},
function () {
$(this).removeClass("result_hover");
}
);
.hoverclass {
height: 72px;
width: 100%;
border: 1px solid #000;
}
.result_hover {
background-color: #000;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="hoverclass">
<div class="item">
<div id="item1">
<i class="icon"></i>Test
</div>
</div>
<div>

Dynamic mouseenter

I appended a few divs with inside img tags. Every tag has own unique id = "theImg"+i where "i" is number. I want to mouseover on specific img and show the content of span (which also have specific id with number). Here is my code so far but not working.
var j;
document.onmouseover = function(r) {
console.log(r.target.id);
j = r.target.id;
}
$(document).on({
mouseover: function(e){
$("span").show();
},
mouseleave: function(e){
$("span").hide();
}
}, "img#"+j);

If you have a span after every img, maybe it's a good idea to not use JavaScript at all? ;-)
You could use :hover pseudoclass in CSS, making your thing always work reliably.
Consider the following example:
img + span {
display: none;
}
img:hover + span {
display: block;
}
/*/ Optional styles /*/
div {
position: relative;
float: left;
}
div img + span {
position: absolute;
color: #fff;
background: #27ae60;
border: solid 1px #2ecc71;
border-radius: 50px;
z-index: 1;
bottom: 1em;
width: 80%;
left: 50%;
margin-left: -43%;
padding: 2% 3%;
text-align: center;
}
<div>
<img src="https://placehold.it/400x200">
<span>This is an image of a gray rectangle!</span>
</div>
<div>
<img src="https://placehold.it/200x200">
<span>This is an image of a gray square!</span>
</div>
<div>
<img src="https://placekitten.com/g/400/200">
<span>This is an image of a cute kitten inside a rectangle!</span>
</div>
<div>
<img src="https://placekitten.com/g/200/200">
<span>This is an image of even cuter kitten inside a square!</span>
</div>

So the issue is that you are trying to set your handler on a dynamic selector ("img#"+j) but this will not work. For one thing, that equation will be evaluated only once, on page load, when j is undefined.
So you want to do this instead:
target only img tags for your mouse over... Better yet, give your special images all the same css class so you can attach the event handlers only to those. That will be more efficient.
When an image is moused over or out of, grab it's id attribute, extract the number from it, then use that to build a selector for the appropriate span to show.
var get_span_from_image = function(image) {
var image_id = image.attr("id");
var matches = image_id.match(/theImg(\d+)/);
if(matches) return $("theSpan" + matches[1]);
return $(); // nothing found, return an empty jQuery selection
};
$("img").hover(
function() { // mouse over
get_span_from_image($(this)).show();
},
function() { // mouse out
get_span_from_image($(this)).hide();
}
);
Note: There are better ways to "link" two nodes together, but this is just to answer your question with the current structure you have.
UPDATE: Some ideas to link two nodes together
So instead of trying to extract a number from an id attribute, a better way would be to tell either one of the image or span about it's sibling. You could output your html like this, for instance:
<img id="theImg1" data-target="theSpan1" class="hoverable" src="..."/>
....
<span id="theSpan1">...</span>
Of course now your ideas could be anything - you don't have to use numbered values or anything.
Then your hover code becomes quite simply:
var get_span_from_image = function(image) {
var span_id = image.data("target");
return $("#" + span_id);
};
$("img").hover(
function() { // mouse over
get_span_from_image($(this)).show();
},
function() { // mouse out
get_span_from_image($(this)).hide();
}
);
Hope this helps!

Targeting previous div in javascript or css

HTML code:
<div class="content">
<textarea> hello.png </textarea>
</div>
<div class="content-btn">
Click me
</div>
Javascript code:
$(".button").click(function() {
if ($(this).parent().previousSibling('.content').css('display') == 'none'){
$('.content').hide();
$(this).parent().previousSibling('.content').show();
}else {
$('.content').hide();
}
});
How would I go about only showing the textarea when 'Cick me' is clicked or hovered preferably in css but if not javascript. Thanks guys
https://jsfiddle.net/uway5hhg/8/

As exercise you could do this effect in pure css (using :target pseudoclass and a long delay in a simple transition) if you add a close button just below the textarea
http://codepen.io/anon/pen/JYoMRK
<div class="content" id="text">
<textarea> hello.png </textarea><br />
Close
</div>
<div class="content-btn">
Open
</div>
CSS
#text {
overflow: hidden;
height: 0;
opacity: 0;
transition: opacity 0s 999999s;
}
#text:target {
opacity: 1;
height: auto;
transition-delay: 0s;
}
#text:target ~ div a.button { display: none; }
Anyway if you look for a straight jQuery approach, a simple toggle() is enough (you might have to hide the .content element via css depending on the initial condition of your textarea)
https://jsfiddle.net/uway5hhg/39/
$(".button").click(function() {
var content = $(this).parent().prev('.content');
content.toggle();
});

As far as I know there is no way to catch previous sibling in CSS.
But it works with jQuery, here is your slightly changed code:
$(".button").on('click', function() {
var ele = $(this),
par = ele.parent(),
sbl = par.prev();
if (sbl.css('display') == 'none'){
$('.content').hide();
sbl.show();
}else {
$('.content').hide();
}
});
Working example is here: https://jsfiddle.net/y0ab3n0L/

That should do it's job
JS:
$(".button").click(function() {
var contentBtn = $(this).parent(".content-btn");
var content = $(contentBtn).prev(".content");
var textarea = $(content).find("textarea");
$(textarea).toggle();
});
or event shorter:
$(".button").click(function() {
$(this).parent(".content-btn").prev(".content").find("textarea").toggle();
});
https://jsfiddle.net/uway5hhg/21/
Hope this helps :)

Solution provided by Fabrizio is a good one if you want no javascript.
However you can also modify the DOM to have a similar effect.
<div class="content-wrapper">
<div class="content" id="text">
<textarea>hello.png</textarea>
</div>
Click me
</div>
CSS
.content {
display:none;
}
.content-wrapper:hover .content {
display:block;
}
.content-wrapper:hover .button {
display:none;
}
https://jsfiddle.net/2Lsszgqz/

There is no such CSS pseudo element - a.button:click, so only JS solution will work (without changing your HTML structure). You can also get to close of it using :focus CSS pseudo class. But you will lack to go up one level in CSS and then show the textarea. So, only solution left is using JS.
In your sample JS code you have used .previousSibling('.content') which is native JS, which you are calling on jQuery object, that's why it will not work. jQuery equivalent of this function is .prev('.content')
Correct Syntax would be -
$(".button").click(function() {
if ($(this).parent().prev('.content').css('display') == 'none'){
$('.content').hide();
$(this).parent().prev('.content').show();
}else {
$('.content').hide();
}
});
Working Fiddle

How to animate inserts and removes in a container with justify-content?

Using the flexbox justify-content property, elements can be distributed evenly in their container. However, I want to animate their positions when a new element is inserted or an existing one is removed.
I only managed to animate the height of the elements so far. However, there is a jump at the end of the animation since the gaps around the removed element that got animated to height: 0 vanish. Analogously, when inserting an element there is a jump at the beginning of the animation.
Is it possible to make an animation from end to end with justify-content? Here is an example to play with. Using CSS transition is preferred.

The main problem is that the behavior you are getting is the expected one.
In the very same instant that card.remove() is executed the flexbox justify-content property need to adjust the gaps around the removed element (as you said). And, as Paulie D has pointed out, there is nothing to animate about.
The only solution I can think about is to skip the flex thing and use javascript to create the necessary gaps among the card elements.
Here I leave the snippet:
var animation_time = 500;
var column_height = $('.column').height();
var cards_height = $('.card').height();
var cards_number;
var cards_total_height;
var space_to_be_distributed;
var placeholder_height;
function updateSizes(cards_number)
{
cards_total_height = cards_number * cards_height;
space_to_be_distributed = column_height - cards_total_height;
placeholder_height = space_to_be_distributed / (cards_number + 1);
}
updateSizes($('.card').length);
$('.placeholder').height(placeholder_height);
$(document).on('click', '.card', function () {
var card = $(this);
card.animate({height: 0, opacity: 0}, animation_time, function () {
card.remove();
});
updateSizes($('.card').length - 1);
var placeholder = card.next();
$('.placeholder').not(placeholder).animate({height: placeholder_height}, animation_time);
placeholder.animate({height: 0}, animation_time, function () {
placeholder.remove();
updateSizes($('.card').length);
$('.placeholder').animate({height: placeholder_height}, animation_time);
});
});
$('a').click(function () {
var card = $('<div class="card">');
card.css({opacity: 0, height: 0})
.appendTo('.column')
.animate({height: 25, opacity: 1}, animation_time);
var placeholder = $('<div class="placeholder">');
placeholder.css({height: 0})
.appendTo('.column');
updateSizes($('.card').length);
$('.placeholder').animate({height: placeholder_height}, animation_time);
});
body, html, .column {
height: 100%;
margin: 0;
}
.column {
float: left;
width: 100px;
background: navy;
overflow: hidden;
}
.card {
height: 25px;
width: 100px;
background: grey;
}
.placeholder {
height: 25px;
width: 100px;
}
<html>
<head>
<script src="http://code.jquery.com/jquery-2.1.3.min.js"></script>
</head>
<body>
<div class="column">
<div class="placeholder"></div>
<div class="card"></div>
<div class="placeholder"></div>
<div class="card"></div>
<div class="placeholder"></div>
<div class="card"></div>
<div class="placeholder"></div>
</div>
Add card
</body>
</html>
Hope it helps!
EDIT - I made the following changes in the code:
I change the fiddle for a SO snippet.
I forced an update of elements size at the end of the animation (in case you click to remove an element before the last one has been completely removed)
I change the size of the elementes to adapt it to the (small) SO snippet window.

jQuery How to Expand AND Collapse Form Field

Target functionality is to expand AND collapse the form field by clicking on the image as seen in the fiddle (http://jsfiddle.net/phamousphil/4jw42kza/). Currently I have expand working using .animate(), however after much fiddling I can't find a way to collapse.
My question is twofold:
1. How can I implement the opposite animation to collapse the form when clicking on the image?
2. (bonus) How can I use .animate() to leverage CSS visibility to fully hide the form when collapsed? My attempt to implement this failed.
Code below:
HTML:
<input class='header-search-box' type='text' id='search-string' name='search-string'>
<img src=' http://findicons.com/files/icons/974/glyphish/18/magnifying_glass.png' class='magnifying-glass' />
CSS:
.header-search-box {
}
.header-search-box {
width: 0px;
}
.magnifying-glass {
}
JavaScript:
$(function(){
var mglass = $('.magnifying-glass');
var form = $('.header-search-box');
mglass.click(function(){
form.animate({'width': '100px'}, 'slow');
});
});

$(function () {
var mglass = $('.magnifying-glass');
var form = $('.header-search-box');
mglass.click(function () {
if (form.is(':hidden')) form.show()
form.animate({
'width': form.width() == 100 ? '0px' : '100px'
}, 'slow', function () {
if (form.width() == 0) form.hide()
});
});
});
jsFiddle example

You can easily achieve it by toggling a 'expanded' class and using CSS3 to handle the animation (and visibility):
CSS:
.header-search-box {
visibility: hidden;
width: 0;
transition: all 0.3s ease;
}
.expanded {
visibility: visible;
width: 100px;
}
JS:
$(function(){
var mglass = $('.magnifying-glass');
var form = $('.header-search-box');
mglass.click(function(){
form.toggleClass('expanded');
});
});
Fiddle here: http://jsfiddle.net/8rLmokp1/