代码：
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>全屏提示框</title> <style> #button{ width: 150px; height: 50px; background-color: greenyellow; } .fullScreenDiv{/* 全屏div */ display: none; position: absolute; left: 0px; top: 0px; width: 100%; height: 100%; background-color: rgba(0, 0, 0, 0.4); } .promptDiv{/* 提示框div */ display: none; position: absolute; left: 50%; top: 50%; transform: translateX(-50%) translateY(-50%); width: 30%; height: 30%; border-radius: 20px; background-color:white; text-align: center; } .close{ height: 34px; line-height: 34px; margin: 0px; text-align: right; border-top-left-radius: 20px; border-top-right-radius: 20px; background-color: cornflowerblue } .X{ padding: 2px 6px; margin-right: 8px; color: white; cursor: pointer; } .countDown{/*倒计时关闭提示框*/ color: red; font-size: 28px; } </style> <script> window.onload=function(){ document.getElementById("button").addEventListener("click",function(){ document.getElementsByClassName("fullScreenDiv")[0].style.display="block"; document.getElementsByClassName("promptDiv")[0].style.display="block"; for(var i=5;i>=0;i--){ (function(i){ setTimeout(function(){ var j=Math.abs(i-5);//如果i为0，那么被定时0s，则要输出abs(0-5)=5 ,如果i为5，那么被定时5s，则要输出abs(i-5)=0 if(j==0){ document.getElementsByClassName("fullScreenDiv")[0].style.display="none"; document.getElementsByClassName("promptDiv")[0].style.display="none"; }else{ document.getElementsByClassName("countDown")[0].innerHTML=j; } },i*1000);//每次间隔时间为1s })(i); } }); document.getElementsByClassName("X")[0].addEventListener("click",function(){ document.getElementsByClassName("fullScreenDiv")[0].style.display="none"; document.getElementsByClassName("promptDiv")[0].style.display="none"; }); } </script> </head> <body> <div> <button>打开全屏提示框</button> </div> <div> <div> <h4><span>X</span></h4> <p>我是全屏提示框我是全屏提示框我是全屏提示框</p> <p>倒计时关闭</p> <span>5</span> </div> </div> </body> </html>