原生javascript禁用和屏蔽鼠标右键

 (function(){
     var doc=document,
         ua = navigator.userAgent.toLowerCase(),
         check = function(r){return r.test(ua);},
         isOpera = check(/opera/),
         isChrome = check(/chrome/),
         isWebKit = check(/webkit/),
         isSafari = !isChrome && check(/safari/),
         isSafari2 = isSafari && check(/applewebkit\/4/),
         isSafari3 = isSafari && check(/version\/3/),
         isSafari4 = isSafari && check(/version\/4/),
         isIE = !isOpera && check(/msie/),
         isIE7 = isIE && check(/msie 7/),
         isIE8 = isIE && check(/msie 8/),
         isIE9 = isIE && check(/msie 9/),
         isIE10 = isIE && check(/msie 10/),
         isIE11 = isIE && check(/msie 11/),
         isIE6 = isIE && !isIE7 && !isIE8 && !isIE9 && !isIE10 && !isIE11,
         isGecko = !isWebKit && check(/gecko/),
         isGecko2 = isGecko && check(/rv:1\.8/),
         isGecko3 = isGecko && check(/rv:1\.9/);
     function preventKey(e) {
         var ev = e || window.event,//获取event对象
         obj = ev.target || ev.srcElement,//获取事件源
         t = obj.type || obj.getAttribute('type'),readonly = obj.readOnly||obj.getAttribute('readonly'), code = ev.keyCode||ev.which||ev.charCode,charcode = String.fromCharCode(code).toLowerCase();//获取事件源控件类型,控件只读属性，键盘值
         if ( (code == 8 && t != "password" && t != "text" && t != "textarea")||(readonly&&(t == "password" || t == "text" || t == "textarea"))) {//除不只读输入框外禁止后退键
             return false;
         }
         if (((isOpera || isGecko)?ev.which==0:true)&&(code == 116 || code == 122|| code == 123 || (ev.shiftKey && code == 121))||(((isOpera || isGecko)?ev.which!=0:true)&&ev.ctrlKey && (charcode == 'a' || charcode == 's'))) {//屏蔽 F5,F11,F12,shift+F10,ctrl+a,ctrl+s
             if (isIE)
                 ev.keyCode = 0;
             ev.returnValue = false;
             return false;
         }
     };
     if (isOpera || isGecko)
         doc.onkeypress = preventKey;
     else if (isIE || isChrome || isSafari)
         doc.onkeydown = preventKey;
     if(isIE)document.onselectstart=function(){return false;};
     doc.oncontextmenu = function(){
         if(window.event){
             window.event.cancelBubble = true;
             window.event.returnValue=false;
         }
         return false;
     };
     try{window.history.forward(1);}catch(e){}
 })();