js firstChild 、nextSibling、lastChild、previousSibling、parentNode

 1         <select><option value="zs">中山</option><option value="gz">广州</option><option value="zh">深圳</option><option value="zh">珠海</option></select>
 2         <script type="text/javascript">
 3               //取得<select>元素节点下的子元素的个数
 4               //var selectElement = document.getElementsByTagName("select")[0];
 5               //var size = selectElement.childNodes.length;
 6               //alert("select下共有"+size+"个元素");
 7               
 8               //取得“中山”字符串
 9               //var selectElement = document.getElementsByTagName("select")[0];
10               //var zsElement = selectElement.firstChild;
11               //var zs = zsElement.innerHTML;
12               //alert(zs);
13               
14               //取得"广州"字符串
15               //var selectElement = document.getElementsByTagName("select")[0];
16               //var zsElement = selectElement.firstChild;
17               //var gzElement = zsElement.nextSibling;
18               //var gz = gzElement.innerHTML;
19               //alert(gz);
20               
21               //取得"珠海"字符串
22               //var selectElement = document.getElementsByTagName("select")[0];
23               //var zhElement = selectElement.lastChild;
24               //var zh = zhElement.innerHTML;
25               //alert(zh);
26               
27               //取得"深圳"字符串
28               //var selectElement = document.getElementsByTagName("select")[0];
29               //var zhElement = selectElement.lastChild;
30               //var szElement = zhElement.previousSibling;
31               //var sz = szElement.innerHTML;
32               //alert(sz);
33               
34               //删除"广州"元素
35               var gzElement = document.getElementsByTagName("option")[1];
36               var selectElement = gzElement.parentNode; 
37               selectElement.removeChild(gzElement);
38               
39               
40               
41               
42         </script>