屏蔽IE浏览器中的功能键

<script>document.onhelp = function(){window.event.returnValue=false;}document.onkeydown=noway;           //绑定窗体加载事件function  noway(){if(window.event.keyCode   ==   113)   { alert("dddd");} if(window.event.keyCode   ==   114)   { window.event.keyCode   =   505; } if(window.event.keyCode   ==   115)   { window.event.keyCode   =   505; } if(window.event.keyCode   ==   116)   { window.event.keyCode   =   505; } if(window.event.keyCode   ==   117)   { window.event.keyCode   =   505; } if(window.event.keyCode   ==   118)   { window.event.keyCode   =   505; } if(window.event.keyCode   ==   119)   { window.event.keyCode   =   505; } if(window.event.keyCode   ==   120)   {   window.event.keyCode   =   505; } if(window.event.keyCode   ==   121)   {   window.event.keyCode   =   505; } if(window.event.keyCode   ==   122)   {   window.event.keyCode   =   505; } if(window.event.keyCode   ==   123)   {   window.event.keyCode   =   505; } if(window.event.keyCode   ==   13)   {   window.event.keyCode   =   505; } if(window.event.keyCode   ==   8)   {   window.event.returnValue=false; } if(window.event.keyCode   ==   505){ window.event.returnValue=false; } }</script>