JS禁止页面刷新

<script type="text/javascript">
        document.onkeydown = function (e) {
        var ev = window.event || e;
        var code = ev.keyCode || ev.which;
        if (code == 116) {
        ev.keyCode ? ev.keyCode = 0 : ev.which = 0;
        cancelBubble = true;
        return false;
        }
        } //禁止f5刷新
        document.oncontextmenu=function(){return false};//禁止右键刷新
    </script>