The querySelectorAll() method run on document returns a list of DOM elements that satisfy the selectors query.

It returns a list of elements, which is not an array but a NodeList object.

The easiest way to loop over the results is to use the for..of loop:

for (const item of document.querySelectorAll('.buttons')) {
  //...do something
}

If you are unfamiliar with the for..of loop I recommend checking out its unique features in my ECMAScript guide.