<html> <head> <meta charset="utf-8"> <title>JS定时器</title> <style type="text/css"> #btn1:hover,#btn2:hover { background: red; } </style> </head> <body> <input type="button" id="btn1" value="开启" /> <input type="button" id="btn2" value="关闭" /> <script> var obtn1=document.getElementById('btn1'); var obtn2=document.getElementById('btn2'); var timer=null; obtn1.onclick=function() { timer=setInterval(function() // Open loop: appears once per second balloon { Alert ( 'A' ); }, 2000 ); } obtn2.onclick = function () { the clearInterval (Timer); // close the loop } </ Script> </ body > </ HTML>