safari Ｆ5禁止使用问题

用以下代码，可以在ＩＥ和ＦＦ下禁止F5,但在safari下Ｆ５仍然可用，请教下
var check=function(e){
keyCode = e.keyCode?e.keyCode:e.which?e.which:e.charCode;
 
if ((keyCode==116)||(e.ctrlKey && keyCode==82)){
　if(!e.which){
　e.keyCode=0;
}
e.cancelBubble = true;
e.returnValue=false;
 
//e.stopPropagation works only in Firefox.
if (e.stopPropagation) {

　 e.stopPropagation();
　 e.preventDefault();
}
}
}
if(document.addEventListener){
document.addEventListener("keydown",check,false);
}else{
document.attachEvent("onkeydown",check);
}

Safari下面的刷新不是Command+R嘛？