CSS - Triangle/Arrow doesn't scroll with its parent container - html

Question

I am trying to have a triangle/arrow at the right of arrow-td. Initial plot with the code below works but the triangle/arrow doesn't scroll with its container arrow-td.
How could I keep the triangle positioned relative to arrow-td even when the user scrolls through main-div?
NOTE: The arrow should stay outside (just right) of main-div. Adding position: relative to arrow-td won't work as that would force arrow to be inside of main-div since overflow-y: auto is activated on main-div.
Check out the plunker
HTML
<div class="main-div">
<table>
<tbody>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td class="arrow-td">
<div class="left-of-arrow">With arrow</div>
<div class="arrow"></div>
</td>
</tr>
.........
</tbody>
</table>
</div>
CSS
.main-div{
height: 200px;
width: 200px;
overflow-y: auto;
}
table{
width: 100%;
max-width: 100%;
}
td{
width: 100%;
background-color: #eee;
display: flex;
}
td>div{
display: flex;
}
.arrow{
right: 300px;
position: absolute;
width: 0;
height: 0;
border-top: 12px solid transparent;
border-bottom: 12px solid transparent;
border-right: 12px solid red;
}

Answer 1

Isn't possible to your arrow track your td without adding a position relative and changing you main-div width to 100% and setting a size to your table, like I did on that plunker
See my Plunker
To do what you wan't you'll need to add a JavaScript function to track the offset of that td every time you scroll the page, and setting the top property of your arrow.
EDIT:
I wasn't in home yesterday, so, I couldn't write a code to solve your issue. I saw your code and there is some issues on your approach. I can't comment there because I don't have karma. But I did some comments on that fork, explaining why those approaches aren't that good.
Updated Plunker

Answer 2

You have your .arrow set with position absolute, meaning it will not be relative to any scrolling you do unless you explicitly specify it to be.
So, by adding position: relative to your .main-div, you will achieve the arrow moving relative to the .arrow-td.
Where your design fails in look and feel is on the .main-div itself. It has a fixed width of 200px. This may be intentional but for your purposes of having the arrow sit outside the table, it will just not be possible using the current HTML structure you have.
One thing you can do is play with how overflow works for your type of problem.
I decided to take a swing at implementing a solution which is what you see below... however the final implementation is truly up to you! I also put in comments a second version of how this could look, in the CSS named Example #2 give it a try :-)
.wrapper {
overflow-y: auto;
width: 335px; /* Example #2: change this to: 100% for a different visual effect */
}
.main-div {
height: 200px;
width: 100%; /* Example #2: change this to 200px for a different visual effect */
}
table {
width: 100%;
max-width: 100%;
}
td {
width: 100%;
background-color: #eee;
display: flex;
}
td > div {
display: flex;
}
.arrow {
left: 300px;
position: absolute;
width: 0;
height: 0;
border-top: 12px solid transparent;
border-bottom: 12px solid transparent;
border-right: 12px solid red;
}
.arrow-td {
position: relative;
}
<div class="wrapper">
<div class="main-div">
<table>
<tbody>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td class="arrow-td">
<div class="left-of-arrow">With arrow</div>
<div class="arrow"></div>
</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
<tr>
<td>Hello</td>
</tr>
</tbody>
</table>
</div>
</div>

Answer 3

This is how I solved the problem through javascript:
I simply track arrow-td's top position, if it is changed .arrow div's top position should also be modified accordingly.
Check out the PLUNKER
Code:
$(document).ready(function(){
setInterval(function(){
var heightLimit = $(".main-div").height();
var parentTop = $(".arrow").parent().position().top;
var arrowTop = $(".arrow").position().top;
//Change arrow top position only if parent's position has been changed
if(arrowTop != parentTop){
if(parentTop < 0 || parentTop > heightLimit -25){
$(".arrow").css("visibility","hidden");
}
else{
$(".arrow").css("visibility","visible");
$(".arrow").css("top",parentTop);
}
}
},500);
});