求帮忙 无法运行
<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>Document</title> <script type="text/javascript"> function showMes(){ alert("hello world"); } var btn1=document.getElementById("btn1"); btn1.attachEvent("onclick",showMes); </script> </head> <body> <input type="button" id="btn1" value="确定" name="按钮1"> </body> </html>