You can add an event listener to all the elements returned by a document.querySelectorAll() call by iterating over those results using the for..of loop:

const buttons = document.querySelectorAll("#select .button")
for (const button of buttons) {
  button.addEventListener('click', function(event) {
    //...
  })
}

It’s important to note that document.querySelectorAll() does not return an array, but a NodeList object.

You can iterate it with forEach or for..of, or you can transform it to an array with Array.from() if you want.