js select 控制实现代码

<select id=test11 size=5 style="width:50px"></select>
<select id="test" style="width:50px"></select>
<button onclick='test[test.length]=new option("1","12");'>同时添加text和value</button>
<button onclick='test.insertbefore(document.createelement("option")).innertext="2";'>对text操作</button> <button onclick='test.appendchild(document.createelement("option")).setattribute("value","3");'>对value操作</button>
<button onclick="alert(test.outerhtml)">view</button>
<button onclick="test.removechild(test.children[0])">del1</button>
<button onclick="test.firstchild.removenode()">del2</button>
<button onclick="test[0]=null">del3</button>