How to achieve the disabling refresh effect in javascript

document.onkeydown = function(e) {
        e = window.event || e;
        var k = e.keyCode;
        //屏蔽ctrl+R，F5键，ctrl+F5键  F3键！验证
        if ((e.ctrlKey == true && k == 82) || (k == 116)
                || (e.ctrlKey == true && k == 116)||k==114) {
            e.keyCode = 0;
            alert("当前页面不能刷新！");
            e.returnValue = false;
            e.cancelBubble = true;
            return false;
        }
        if (k == 8) {
            alert("不能返回或后退！");
            e.keyCode = 0;
            e.returnValue = false;
            return false;
        }
        //屏蔽 Ctrl+n   验证可以实现效果
        if (e.ctrlKey && k == 78){
            e.keyCode = 0;
            e.returnValue = false;
            e.cancelBubble = true;
            return false;
            }
        //屏蔽F11   验证可以实现效果
        if (k == 122) {
            e.keyCode = 0;
            e.returnValue = false;
            e.cancelBubble = true;
            return false;
        }
        //屏蔽 shift+F10  验证可以实现效果      
        if ((e.shiftKey && k == 121)||(e.ctrlKey && k == 121)){
            e.keyCode = 0;
            e.returnValue = false;
            e.cancelBubble = true;
            return false;
            }
        //屏蔽Alt+F4  
        if ((e.altKey) && (k== 115)) {
            window.showModelessDialog("about:blank", "",
                    "dialogWidth:1px;dialogheight:1px");
            e.keyCode = 0;
            e.returnValue = false;
            e.cancelBubble = true;
            return false;
        }
        //屏蔽 Alt+ 方向键 ← ;屏蔽 Alt+ 方向键 → ！验证
        if ((e.altKey)
                && ((k == 37) || (k == 39))) {
            alert("不准你使用ALT+方向键前进或后退网页！");
            e.keyCode = 0;
            e.returnValue = false;
            e.cancelBubble = true;
            return false;
        }
    };
    
    //屏蔽右键菜单，！验证
    document.oncontextmenu = function(event) {
        if (window.event) {
            event = window.event;
        }
        try {
            var the = event.srcElement;
            if (!((the.tagName == "INPUT" && the.type.toLowerCase() == "text") || the.tagName == "TEXTAREA")) {
                return false;
            }
            return true;
        } catch (e) {
            return false;
        }
    };