JSFiddle - React, Tailwind, and code Playground

HTML

<nav>
  <div class="sidebar-item">Пункт 1</div>
  <div class="sidebar-item">Пункт 2</div>
  <div class="sidebar-item">Пункт 3</div>
  <div class="sidebar-item">Пункт 4</div>
  <div class="sidebar-item">Пункт 5</div>
</nav>

CSS

nav {
  display: flex;
}
.sidebar-item {
  margin: 0 20px;
  padding: 5px 20px;
  border: 1px solid #ccc;
  background: yellow;
  cursor: pointer;
}
.selected {
  background: #ff0000;
  color: #fff;
}

JavaScript

var menuItems = document.getElementsByClassName("sidebar-item");

  for (var i = 0; i < menuItems.length; i++) {
  
          menuItems[i].addEventListener("click", function() { 
          
          this.classList.add('selected');
                 
      });
  }