<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>document</title> <style> body, html { height: 100%; } div { display: fixed; left: 0; right: 0; top: 0; bottom: 0; margin: auto; height: 300px; width: 500px; line-height: 300px; text-align: center; background-color: #ccc; margin-top: 100px; } div span { color: red; } </style> </head> <body> <div id="ads"> <h1>这是一则广告,在<span id="count5s">5</span>秒后自动关闭!</h1> </div> <script> function closeAds() { document.getElementById('ads').style.display = "none"; } var oCount5s = document.getElementById("count5s").innerText var second = parseInt(oCount5s) function countDown() { second -= 1; document.getElementById("count5s").innerText = second; } var countDown = setInterval(countDown, 1000) setInterval(function () { if (second === 0) { closeAds(); clearInterval(countDown); } }, 1000) </script> </body> </html>