监听键盘按下键的值（兼容IE与其他浏览器）
function getKeyPressCode(event) {
/*
//此种方法不可取
if(event.keyCode!=0) // IE
{
keynum = event.keyCode;
}
else if(event.which!=0) // Netscape/Firefox/Opera
{
keynum = event.which;
}
alert(keynum);
*/
//此种方法可行
var keycode;
if (navigator.appName == "Microsoft Internet Explorer") { // IE
keycode = event.keyCode;
} else { // Netscape/Firefox/Opera
keycode = event.which;
}
alert("按键码: " + keycode );
}