JS如何实现剪贴板里自动加上版权出处

<script>
function addLink() {
    var body_element = document.body;
    var selection;
    var blogName = '网站名称';
    selection = window.getSelection() ? window.getSelection() : document.selection.createRange().text;
    if (window.clipboardData) {
        var pagelink ="<br/>---------------------<br/>"+"<br/>原文地址："+document.location.href+"";
        var copyText = selection + pagelink;
        window.clipboardData.setData ("Text", copyText);
        return false;
    } else {
        var pagelink = "<br/>---------------------<br/>"+"<br/>原文地址："+document.location.href+"";
        var copyText = selection + pagelink;
        var newDiv = document.createElement('div');
        newDiv.style.position ='absolute';
        newDiv.style.left ='-123456789px';
        body_element.appendChild(newDiv);
        newDiv.innerHTML = copyText;
        selection.selectAllChildren(newDiv);
        window.setTimeout(function() {
            body_element.removeChild(newDiv);
        },0);
    }
}
document.oncopy = addLink;
  </script>