js 实现网页强制复制内容

<script type="text/javascript">
<!--
document.body.oncopy = function () {
        setTimeout( function () {
                var text = clipboardData.getData("text");
                if (text) {
                        text = text + "(本内容来自查询系统 http://www.yidongqu.com 原文地址："+location.href+')';
clipboardData.setData("text",text);
                }
                                }, 100 )

}
 -->
</script>