屏蔽F5 右键 火狐 和 IE的写法

window.event is undefined
原因是火狐不兼容
<script language="Javascript">   

	document.oncontextmenu = function() {
		return false;
	};
	document.ondragstart = function() {
		return false;
	};
	document.onselectstart = function() {
		return false;
	};
	document.onbeforecopy = function() {
		return false;
	};
	document.onselect = function() {
		document.selection.empty();
	};
	document.oncopy = function() {
		document.selection.empty();
	};
	document.onmouseup = function() {
		document.selection.empty();
	};

	function DisableF5() {
		with (event) {
			// F5 and Ctrl+R
			if (keyCode == 116 || (ctrlKey && keyCode == 82)) {
				event.keyCode = 0;
				event.cancelBubble = true;
				return false;
			}
		}
	}
	document.onkeydown = DisableF5;
	var check=function(e){
		   e=e||window.event;
		   //alert(e.which||e.keyCode);
		   if((e.which||e.keyCode)==116){
		    if(e.preventDefault){
		    e.preventDefault();}
		    else{event.keyCode = 0;
		     e.returnValue=false;}
		   }
		};
		if(document.addEventListener){
		   document.addEventListener("keydown",check,false);
		}
		else{
		   document.attachEvent("onkeydown",check);
		}

</script>