Element activation in JavaScript

Suppose we have some HTML table #table with empty cells.

Let's make it so that when you click on any cell, it is somehow activated, for example, it gets a red background. To do this, we will add some CSS class to activated cells:

css.active {
  background: red;
}

Let's implement activation:

javascriptlet tds = document.querySelectorAll('#table td');

for (let td of tds) {
  td.addEventListener('click', function() {
    this.classList.add('active');
  });
}