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How to dynamically get the length of a div using JQuery and JavaScript?

I am developing a web application using AngularJS. I find myself in a situation where I have a bar (with the css I created a line) that must dynamically lengthen and shorten.
I know that JQuery scripts are sufficient to do this. For example, if my css is like this:
.my_line{
display:block;
width:2px;
background: #FFAD0D;
height: 200px; /*This is the part that needs to dynamically change*/
}
I could in the controller resize the line (of my_line class) simply with:
$(".my_line").css("height", someExpression*100 + 'px');
The thing is, I would like to dynamically resize the line based on the size of another div element (Or, in general, any HTML element of my choice).
I don't know how to get (at run-time) the size of a certain page element in terms of height.
Only in this way I would be able to create a line that dynamically lengthens or shortens as the size of a div (or some other element) changes!
How do you do this? So I will avoid writing hard-coded the measures but I want make sure that they vary as the dimensions of other elements on the page vary

I hope this is helping:
$(".my_line").css("height", $("#referenceElement").height()*5 + 'px');
.my_line{
display:inline-block;
width:2px;
background: #FFAD0D;
}
#referenceElement {
display:inline-block;
background: yellow;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div class="my_line"></div>
<div id="referenceElement">Hi, I'm 5 time smaller than the orange line!</div>

Here I am using the setInterval to track the div's height (you can do width as well) and storing it in a previousHeight variable and comparing it every interval
Then according to the comparison, it will determine if the height of the div has changed. If it has then it will change the height of the other div according to the height of the first div
You can create multiple variables and track multiple elements in the same setInterval
$(document).ready(function(){
var previousHeight = parseInt($("#my-div").css("height"));
setInterval(function(){ checkHeight(); }, 100);
function checkHeight() {
// Check height of elements here
var currentHeight = parseInt($("#my-div").css("height"));
if(currentHeight != previousHeight) {
previousHeight = currentHeight;
$("#dynamic-div").css("height", parseInt(currentHeight) + "px");
}
}
$("#button").click(function() {
$("#my-div").css("height", parseInt(previousHeight) + 5 + "px");
})
})
#my-div{
background: #000000;
height: 20px;
width: 20px;
}
#dynamic-div{
background: teal;
height: 20px;
width: 20px;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div id="my-div">
</div>
<button id="button">Increase div height</button>
<div id="dynamic-div">
</div>

JS. Detect hidden child with parent overflow:hidden

I'm looking for simple way to detect, if child element of parent with overflow:hidden is visible within parent (it's not hidden by overflow).
I found something like this:
http://www.useallfive.com/thoughts/javascript-tool-detect-if-a-dom-element-is-truly-visible/
but i wonder maybe there is simpler solution.
Thanks in advance!

Assuming you want a vanilla js solution, try this:
function isVisible (parent, child) {
return !(
(child.offsetLeft - parent.offsetLeft > parent.offsetWidth) ||
(child.offsetTop - parent.offsetTop > parent.offsetHeight)
)
}
Basically "if the difference between the start of the parent element and the start of the child element is greater than the actual width or height of the parent, it's considered not visible"
Run the following snippet for an example:
var parent = document.getElementById('parent');
[].slice.call(document.querySelectorAll('.child')).forEach(function (child, i) {
console.log(i + ' is visible?', isVisible(parent, child));
});
function isVisible(parent, child) {
return !(
(child.offsetLeft - parent.offsetLeft > parent.offsetWidth) ||
(child.offsetTop - parent.offsetLeft > parent.offsetHeight)
)
}
* {
box-sizing: border-box;
}
#parent {
width: 200px;
height: 100px;
white-space: nowrap;
background: lightblue;
}
.child {
display: inline-block;
width: 75px;
height: 100%;
border: 1px solid green;
}
<div id="parent">
<div class="child">0</div>
<div class="child">1</div>
<div class="child">2</div>
<div class="child">3</div>
<div class="child">4</div>
</div>

You can do the following things:
check if the element has height and width that are bigger than 0px
check if the element display CSS property is not "none", preferably "block"
check if the element positioning is valid and if so, check if it´s "top" property is not bigger than the parent´s height
Same thing for left - if it is not bigger than parent´s width
When checking "width", check offsetWidth and clientWidth, those will show actual numbers as displayed to the client.

I had a similar requirement, but mine was a bit more complicated because the overflow: hidden element wasn't the first parent, it was like 5 or 6 elements away.
Just spend a whole day trying to do it with solutions from the internet(I've tried the repo you mentioned as well), but nothing worked.
So I've made this repo by myself (only JS, 2kb sized) https://github.com/LuizAsFight/is-element-visible.
It might help you, basically I just get the target element and climb the tree searching if any parent has a overflow:hidden, once I found it I get the parent's rect size, and check if the target element rect is inside the parent (visually, pixels)
for using it you just need to
import isVisible from 'is-element-visible';
const el = document.getElementById('id');
isVisible(el);
I hope it helps you, Best.

How can I make the parent div draggable

I have a div containing three buttons. The div needs to be draggable, so that you can drag all three buttons around the screen together. That works fine, but the problem is that when I click on of the individual buttons it inherits the draggable id and it is draggable on it's own. I do not want that to happen. So my question is: how do I make my buttons draggable, but make them always stay together and keep them clickable. I added the code below, but here is a JSFiddle: http://jsfiddle.net/2ga50vvt/
So to be clear: the div also needs to be draggable through dragging one of the individual buttons, but then the rest of the div needs to stick with it. Now dragging an individual button only moves the button.
P.S. I do not want to use JQuery UI
HTML:
<div id="draggable" class="ui-widget-content">
<button ng-click="menu.shown = !menu.shown">MENU</button>
<br>
<button ng-click="disconnect()">CLOSE</button>
<br>
<button ng-click="">KEYS</button>
</div>
JS
$(document).ready(function() {
var $dragging = null;
$('body').on("mousedown", "#draggable", function(e) {
$(this).attr('unselectable', 'on').addClass('dragged');
var el_w = $('.dragged').outerWidth(),
el_h = $('.dragged').outerHeight();
$('body').on("mousemove", function(e) {
if ($dragging) {
$dragging.offset({
top: e.pageY - el_h / 2,
left: e.pageX - el_w / 2
});
}
});
$dragging = $(e.target);
}).on("mouseup", ".dragged", function(e) {
$dragging = null;
$(this).removeAttr('unselectable').removeClass('dragged');
});
});
CSS:
body {
padding: 50px;
}
.dragged {
background-color: yellow;
}
#draggable {
position: fixed;
width: 150px;
height 150px;
padding: 0.5em;
background: red;
background-color: black;
z-index: 1000;
cursor: move;
float: left;
}
Update 1
This is a working solution: http://jsfiddle.net/2ga50vvt/3/
However when I click on the div and start dragging the center of the div jumps to my cursor. It works great, but it looks a bit wonky. Is there a way to prevent the div from moving to my cursor?
Your help is most welcome.

You can read the target property of the event and return false to avoid all not #draggable to be draggable.
if(e.target.id !== "draggable") {
return false;
}
The edited fiddle:
http://jsfiddle.net/2ga50vvt/1/
It works perfectly, but one suggestion: don't target with ids because with this code you can't drag more of one element (ids must be unique), so the workaround is to write an attribute or a classname and play with it.
Good luck.

Use $dragging = $('#draggable'); instead of $dragging = $('e.target');
It will drag div if you try to drag using cursor on button. It will drag #draggable instead of target.
Working Fiddle

Presuming you're opposed to JQueryUI for it's file size, I'd still recommend a prebuilt solution because why reinvent the wheel?
Draggabilly is a really nifty library that I've used when resource size has been an issue. It's 20k minified (obviously even smaller gzipped) and available on a CDN - which in itself has lots of benefits e.g. caching.
$(function() {
$( "#draggable" ).draggabilly();
});
There's a few CSS hooks, different options, events etc.
JSFiddle here

jQuery UI: Container div resizes

In the following example there are two draggable divs in a container div. When the second draggable div is removed (by clicking on the button) the first div moves up and the container is resized (see jsfiddle). The first div should not move when the second div is removed, as its position is absolute. What's wrong with this code?
The HTML:
<div id="container" style="background-color:blue;width:100%;height:100%"></div>
<button onclick="removeDiv()">Remove</div>
and the javascript:
$(document).ready(function(){
var $div0 = $('<div id="div0" />').appendTo('#container');
$div0.draggable();
$div0.offset({ top: 200, left: 350});
$div0.css('background-color','white');
$div0.css('width','150px');
$div0.css('height','200px');
$div0.text(0);
var $div1 = $('<div id="div1" />').appendTo('#container');
$div1.draggable();
$div1.offset({ top: 200, left: 50});
$div1.css('background-color','white');
$div1.css('width','150px');
$div1.css('height','200px');
$div1.text(1);
});
function removeDiv () {
$('#div0').remove();
}

Both draggable divs have relative positions. You can fix them up like so:
http://jsfiddle.net/isherwood/dzSRR/13/
#container {
position: relative;
}
#container > div {
position: absolute;
}
Because they're now absolutely-positioned, you'll need to give the parent div a height. If you use 100%, you also need to apply that height to html, body.
http://jsfiddle.net/isherwood/dzSRR/14/

duplicate div then do a horizontal scroll

I'm trying to clone #main then put my ajax result there (hidden), after doing so I will make it scroll horizontally to the left hiding the current one then display the clone.
HTML:
<div class="container">
<div id="main">
<p>Click here to start</p>
</div>
</div>​
CSS:
#main{
width:460px;
min-height:200px;
background:#3F9FD9;
margin:0 auto;
}
.container {
position:relative;
}
​
Javascript:
$('#main').click(function(){
//clone.html(data)
var clone = $(this).clone().html('<p>Ajax loaded content</p>').css(
{position:'absolute',right:'0','margin-right':'-460px',top:0}
).attr('class','love').insertAfter($(this));
$(this).css({position:'relative'});
var width = $(window).width()-$(this).outerWidth()/2;
$('#main').animate({'left':'-'+width},4000);
});
but i'm stuck on the idea on how to make both #main animate to the left and position the second div at the center?
Fiddle
EDIT: Now i'm only stuck on how to animate the clone.

I sort of took a different approach to your question, is this kind of what you are looking for?
http://jsfiddle.net/3s7Fw/5/show
I thought, rather than do some animating ourselves, why not let jQuery's hide function do it for us? This could definitely be made to work better, but it communicates the thought.
JavaScript
$('.container').on('click', '.loaded-content', function(){
$this = $(this);
//clone.html(data)
var clone = $this.clone().html('<p>Ajax loaded content</p>').attr("id", '');
$this.after(clone);
$this.hide('slow');
});​
HTML
<div class="container">
<div id="main" class="loaded-content">
<p>Click here to start</p>
</div>
</div>​
CSS
#main, .loaded-content{
width:460px;
min-height:200px;
background:#3F9FD9;
margin:0 auto;
float: left;
}
.container {
position:relative;
width: 920px;
}
​If this is not the desired functionality, then you might be interested in a slider. There are a number of good slider plugins already out there that you can use. The difficult part would probably be adding a addNewSlide function to your chosen slider, assuming it didn't already have one.