js copyboardDate 跨浏览器

function copyToClipboard(txt) {  
         if(window.clipboardData) {  
                 window.clipboardData.clearData();  
                 window.clipboardData.setData("Text", txt);  
         } else if(navigator.userAgent.indexOf("Opera") != -1) {  
              window.location = txt;  
         } else if (window.netscape) {  
              try {  
                   netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");  
             } catch (e) {  
                  alert("被浏览器拒绝！\n请在浏览器地址栏输入'about:config'并回车\n然后将'signed.applets.codebase_principal_support'设置为'true'");  
             }  
             var clip = Components.classes['@mozilla.org/widget/clipboard;1'].createInstance(Components.interfaces.nsIClipboard);  
             if (!clip)  
                  return;  
             var trans = Components.classes['@mozilla.org/widget/transferable;1'].createInstance(Components.interfaces.nsITransferable);  
             if (!trans)  
                  return;  
             trans.addDataFlavor('text/unicode');  
             var str = new Object();  
             var len = new Object();  
            var str = Components.classes["@mozilla.org/supports-string;1"].createInstance(Components.interfaces.nsISupportsString);  
             var copytext = txt;  
             str.data = copytext;  
             trans.setTransferData("text/unicode",str,copytext.length*2);  
             var clipid = Components.interfaces.nsIClipboard;  
             if (!clip)  
                  return false;  
             clip.setData(trans,null,clipid.kGlobalClipboard);  
             
        }  
      
   }