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; } };