JavaScript : add text when copying content

function addtext()
{
    var text = "<br /><br />Read more at www.arkanite.com";
    var body = document.getElementsByTagName('body')[0];
    var selection = window.getSelection();
    var div = document.createElement('div');
    for (var i=0; i<selection.rangeCount;++i)
        div.appendChild(selection.getRangeAt(i).cloneContents());
    var copytext = div.innerHTML+text;
    var newdiv = document.createElement('div');
    newdiv.style.position='absolute';
    newdiv.style.top='-9999px';
    body.appendChild(newdiv);
    newdiv.innerHTML = copytext;
    selection.selectAllChildren(newdiv);
    window.setTimeout(function()
    {
        body.removeChild(newdiv);
    }, 0);
}
document.oncopy = addtext;