浏览器好像不允许js获取F5这个键的按下事件，应该屏蔽了，这个键太过特殊，猜测可能是，防止用户失去对浏览器的控制？
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<title></title>
<meta charset="utf-8" />
</head>
<body onkeypress="checkKey(event)">
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<script type="text/javascript">
function checkKey(event) {
keynum = window.event ? event.keyCode : event.which;
keychar = String.fromCharCode(keynum);
alert(keynum + ':' + keychar);
console.log(event);
console.log(this)
//alert("event");
if (keynum == 116) {
alert("想刷新？");
return false;
}
}
</script>
</body>
</html>