HTML/CSS/JS在单击时更改多个按钮的颜色

<button id="button1">Button 1</button>
<button id="button2">Button 2</button>
<button id="button3">Button 3</button>

button {
  background-color: #ccc;
}

button.clicked {
  background-color: #ff0000;
}

var button1 = document.getElementById("button1");
var button2 = document.getElementById("button2");
var button3 = document.getElementById("button3");

button1.addEventListener("click", function() {
  button1.classList.add("clicked");
});

button2.addEventListener("click", function() {
  button2.classList.add("clicked");
});

button3.addEventListener("click", function() {
  button3.classList.add("clicked");
});