# 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:

`.active { background: red; }`

Let's implement activation:

`let tds = document.querySelectorAll('#table td'); for (let td of tds) { td.addEventListener('click', function() { this.classList.add('active'); }); }`

Given an HTML list `ul`. Make it so that when you click on any item in the list, it is activated with a red background.

Modify the previous task so that by clicking on the activated list item, activation is removed from it.

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