如何检测DOM准备并添加没有jQuery的类？

document.addEventListener("DOMContentLoaded", function() {
  // 在这里添加您的代码
});

document.addEventListener("DOMContentLoaded", function() {
  var element = document.getElementById("your-element-id");
  element.classList.add("your-class-name");
});

document.addEventListener("DOMContentLoaded", function() {
  var element = document.getElementById("your-element-id");
  element.classList.add("your-class-name");
});