js复制

        <script type="text/javascript">
      //复制
            function copytxt() {
                alert("进入该函数。");
                var txt = "";
                if (window.getSelection) {
                    txt = window.getSelection();
                }
                else if (document.getSelection) {
                    txt = document.getSelection();
                }
                else if (document.selection) {
                    txt = document.selection.createRange().text;
                }
                copyToClipboard(txt);
            }
            //粘贴
            function pastetxt() {
                var ta = document.getElementById("selectedtext");
                ta.focus();
                ta.document.execCommand("paste"); // 粘贴
            }
            //复制到粘贴板函数
            function copyToClipboard(txt) {
                if (window.clipboardData) {
                    window.clipboardData.clearData();
                    window.clipboardData.setData("Text", txt);
                }
            }
        </script>