javascript 实现左移右移上移下移（厦门_小鱼儿_^1^）

<script language="JavaScript"><!--function moveOption(e1, e2){try{for(var i=0;i<e1.options.length;i++){if(e1.options[i].selected){var e = e1.options[i];e2.options.add(new Option(e.text, e.value));e1.remove(i);i=i-1}}document.myform.city.value=getvalue(document.myform.list2);}catch(e){}}function getvalue(geto){var allvalue = "";for(var i=0;i<geto.options.length;i++){allvalue +=geto.options[i].value + ",";}return allvalue;}function changepos(obj,index){if(index==-1){if (obj.selectedIndex>0){obj.options(obj.selectedIndex).swapNode(obj.options(obj.selectedIndex-1))}}else if(index==1){if (obj.selectedIndex<obj.options.length-1){obj.options(obj.selectedIndex).swapNode(obj.options(obj.selectedIndex+1))}}}//--></script>HTML代码片段<form method="post" name="myform"><table border="0" width="300"><tr><td width="40%"><select style="WIDTH:100%" multiple name="list1" size="12" ondblclick="moveOption(document.myform.list1, document.myform.list2)"><option value="北京">北京</option><option value="上海">上海</option><option value="山东">山东</option><option value="安徽">安徽</option><option value="重庆">重庆</option><option value="福建">福建</option><option value="甘肃">甘肃</option><option value="广东">广东</option><option value="广西">广西</option><option value="贵州">贵州</option><option value="海南">海南</option><option value="河北">河北</option><option value="黑龙江">黑龙江</option></select></td><td width="20%" align="center"><input type="button" value="添加" onclick="moveOption(document.myform.list1, document.myform.list2)"><br/><br/><input type="button" value="删除" onclick="moveOption(document.myform.list2, document.myform.list1)"></td><td width="40%"><select style="WIDTH:100%" multiple name="list2" size="12" ondblclick="moveOption(document.myform.list2, document.myform.list1)"></select></td><td><button onclick="changepos(list2,-1)" type="button">上移</button><br/><button onclick="changepos(list2,1)" type="button">下移</button></td></tr></table>值：<input type="text" name="city" size="40"></form>