<html> <head> <meta charset="utf-8"> <title>JS定時器</title> <style type="text/css"> #btn1:hover,#btn2:hover { background: red; } </style> </head> <body> <input type="button" id="btn1" value="開啟" /> <input type="button" id="btn2" value="關閉" /> <script> var obtn1=document.getElementById('btn1'); var obtn2=document.getElementById('btn2'); var timer=null; obtn1.onclick=function() { timer=setInterval(function() //開啟循環：每秒出現一次提示框 { alert('a'); },2000); } obtn2.onclick=function() { clearInterval(timer); //關閉循環 } </script> </body> </html>