How to change the background of the active item in the menu?

Question

css

How to make the background of an item in the menu appear when we are on a particular page. For example, we are on the 'Home', and in the menu the background of the 'Home' has changed. For example, as in the menu of this site.
The active item is the item that points to the page we are on.
P.S. I'm sorry for explaining so badly.

Answer 1

It can be implemented in Javascript if it's just layout, without using CMS.
If this is a CMS, then it has an active class on the navigation item related to different pages.
js will look like this

var urlNow = window.location.pathname.split('/').join(' ');
$(".nav a").each(function(){
  var hrefLink = $(this).attr('href');
  var findConsilience = urlNow.indexOf(hrefLink);
  if(findConsilience > 0){
    $(this).addClass('item-active');
  }
});

html so
url
somesite/contacts.html