用Html,css,javascript创建3秒后自动关闭的banner

HTML代码

<div id="banner">
  <p>This is a self-closing banner.</p>
  <button id="close-banner">X</button>
</div>

css代码

#banner {
  background-color: #f1f1f1;
  padding: 10px;
  position: fixed;
  bottom: 0;
  left: 0;
  width: 100%;
  text-align: center;
  z-index: 999;
}
#close-banner {
  position: absolute;
  top: 10px;
  right: 10px;
  background-color: #f44336;
  color: white;
  font-weight: bold;
  padding: 5px 8px;
  border-radius: 50%;
  cursor: pointer;
}

Javascript代码

// set a timeout to close the banner after 3 seconds
setTimeout(function(){
    var banner = document.getElementById("banner");
    banner.style.display = "none";
}, 3000);

// add an event listener to the close button
var closeButton = document.getElementById("close-banner");
closeButton.addEventListener("click", function() {
    var banner = document.getElementById("banner");
    banner.style.display = "none";
});

JavaScript使用setTimeout函数在3秒（3000毫秒）后关闭横幅，方法是将横幅元素的显示属性设置为“none”。它还使用addEventListener将一个单击事件附加到关闭按钮，该按钮也通过在单击时将banner元素的显示属性设置为“none”来关闭横幅。