在至少选中三个输入复选框(每组六个)之前，如何隐藏按钮？

// HTML
<input type="checkbox" id="checkbox1">
<input type="checkbox" id="checkbox2">
<input type="checkbox" id="checkbox3">
<button id="myButton">按钮</button>

// JavaScript
var checkbox1 = document.getElementById("checkbox1");
var checkbox2 = document.getElementById("checkbox2");
var checkbox3 = document.getElementById("checkbox3");
var myButton = document.getElementById("myButton");

checkbox1.addEventListener("change", hideButton);
checkbox2.addEventListener("change", hideButton);
checkbox3.addEventListener("change", hideButton);

function hideButton() {
  var checkedCount = 0;
  if (checkbox1.checked) checkedCount++;
  if (checkbox2.checked) checkedCount++;
  if (checkbox3.checked) checkedCount++;

  if (checkedCount >= 3) {
    myButton.style.display = "block";
  } else {
    myButton.style.display = "none";
  }
}

<style>
  .hidden {
    display: none;
  }
</style>

<input type="checkbox" id="checkbox1">
<input type="checkbox" id="checkbox2">
<input type="checkbox" id="checkbox3">
<button id="myButton" class="hidden">按钮</button>

<script>
  var checkbox1 = document.getElementById("checkbox1");
  var checkbox2 = document.getElementById("checkbox2");
  var checkbox3 = document.getElementById("checkbox3");
  var myButton = document.getElementById("myButton");

  checkbox1.addEventListener("change", hideButton);
  checkbox2.addEventListener("change", hideButton);
  checkbox3.addEventListener("change", hideButton);

  function hideButton() {
    var checkedCount = 0;
    if (checkbox1.checked) checkedCount++;
    if (checkbox2.checked) checkedCount++;
    if (checkbox3.checked) checkedCount++;

    if (checkedCount >= 3) {
      myButton.classList.remove("hidden");
    } else {
      myButton.classList.add("hidden");
    }
  }
</script>