オリジナルJavaScript書き込みselectドロップダウン選択後ジャンプページ

 1 <select name="molsel_oprate" onchange="javascript:var obj = event.target; var index = obj.selectedIndex; $(this).val('default');var linkurl = obj.options[index].getAttribute('linkurl');if(index == 3){location.href=linkurl;}else{window.open(linkurl);}">
 2 
 3 <option value="default"> option>
 4  <option linkurl="aaa"> <span class="layui-icon" onclick="seledoplmki()"> span>
 5 option>
 6 
 7  <option linkurl="bbb"> <span class="layui-icon" > span>
 8 option>
 9 
10  <option linkurl="ccc" style="text-decoration:none"><span class="layui-icon"> span>
11 option>
12 select>