<dd>
                                <span>出发城市</span> 
                                <a id="StartAll" class="all" href="javascript:void(0);" title="all" onclick="jurney('0','','','','','',247,'StartAll');">全部</a>
                                <a id="Start1"  href="javascript:void(0);" onclick="jurney('{dede:php}echo urlencode('深圳');{/dede:php}','','','','','',247,'Start1')">深圳</a>
                                <a id="Start2" href="javascript:void(0);" onclick="jurney('{dede:php}echo urlencode('广州');{/dede:php}','','','','','',247,'Start2')">广州</a>
                                <a id="Start3" href="javascript:void(0);" onclick="jurney('{dede:php}echo urlencode('北京');{/dede:php}','','','','','',247,'Start3')">北京</a>
                                <a id="Start4"  href="javascript:void(0);" onclick="jurney('{dede:php}echo urlencode('成都');{/dede:php}','','','','','',247,'Start4')">成都</a></dd>
HTML代码如上,我已经用 str=document.getElementsByTagName("dd")[0].innerHTML; 获得了 <dd> 这个标签的集合的第一个元素也就是以上的代码里面的innerHTML,但是我现在要获得<dd>[0] 里面的所有 <a> 标签的集合,请问如何写?