Angular get current focused element in angular - css

Question

I have a website I am trying to do something like this, when I click on 1, I want the background of this element to change to white and when I click on the second one the background of the first one will disappear and pass to the next one...I have been trying to do this for a long time help me I don't know how to do it
<div class="oval">1</div>
<div class="oval">2</div>
<div class="oval">3</div>

Answer 1

When we need make "something" exclusive we use one unique variable
selectedIndex:number=-1
If you want not unselected
<div class="oval" [class.selected]="selectedIndex==0"
(click)="selectedIndex=0">
1
</div>
<div class="oval" [class.selected]="selectedIndex==1"
(click)="selectedIndex=1">
2
</div>
<div class="oval" [class.selected]="selectedIndex==2"
(click)="selectedIndex=2">
3
</div>
If you want unselected
<div class="oval" [class.selected]="selectedIndex==0"
(click)="selectedIndex=selectedIndex==0?-1:0">
1
</div>
<div class="oval" [class.selected]="selectedIndex==1"
(click)="selectedIndex=selectedIndex==1?-1:1">
2
</div>
<div class="oval" [class.selected]="selectedIndex==2"
(click)="selectedIndex=selectedIndex==2?-1:2">
3
</div>
NOTE: I use [class.selected], so we use a .css
.selected{
background:red;
}
You can use style.background or style.background-color using (condition)?value:null, e.g., for the first div
[style.background]="selectedIndex==0?'red':null

Answer 2

Like #Kwright02's comment you can do it with css:
.myclass:focus {
background-color: green;
}
But important: The element must be focusable. So a div isn't, a button is as example.
Second way (add a click handler and change the background directly):
// HTML
<div (click)="onClick($event)">test</div>
// Code
onClick(event: any) {
event.target.style["background-color"] = "green";
}
Note: This is not the way to go in Angular. Here use property binding and bind a style to a condition as example.
Instead of add a click listener to each control you can use Angular's HostListener like this:
#HostListener("document:click", ["$event"])
onAllClick(event: any) {
event.target.style["background-color"] = "green";
}