JS copy to clipboard sample code_javascript skills

/*
* Copy to clipboard
*
* */

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) {
showAlert("Rejected by browser! Please enter 'about:config' in the browser address bar and press Enter Then set 'signed.applets.codebase_principal_support' to '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);
showMessage("Copy successfully!");
}else if(window.navigator.userAgent.indexOf("Chrome") !== -1 ) {
var dialog = $("#sanwn_clipboardDialog");
if(dialog.length==0){
var text = "";
$("body").append( $ (text));
$("#sanwn_clipboardDialog").omDialog({
autoOpen: false,
height: 140,
modal: true
});
dialog = $( "#sanwn_clipboardDialog");
}
$("#sanwn_clipboardTxt").val(txt);

$("#sanwn_clipboardDialog").omDialog("open");
document.getElementById("sanwn_clipboardTxt").select();
}
}