var doc = obj.createTextRange();
doc.select();
doc.execCommand('copy');

if(window.clipboardData) //IE
{
window.clipboardData.clearData();
window.clipboardData.setData("Text", txt);
}
else if (window.netscape)
{
try { netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
}
catch (e)
{
alert("please visit 'about:config' and set signed.applets.codebase_principal_support as 'true'");
//提示用戶開放瀏覽器的安全性設置
}

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;
　　　　　　 clip.setData(trans,null,clipid.kGlobalClipboard);
}