javascript 小技巧

<!-- 另存为图片 -->
                                    <input type="button" value="下载" onclick="download()"/>
                                    <iframe   src="../images/sm2.gif"   name="show"   style="width:0;height:0"></iframe>
                                    <script language="javascript">
                                    function download(){
                                       show.document.execCommand("SaveAs");
                                        }
                                    </script>
                                    <!-- 另存为图片 -->