jQuery取得设置清空select选择的文本与值

<option value="1">选项1</option>
<option value="2">选项2</option>
<option value="3">选项3</option>
<option value="4">选项4</option>
<option value="5">选项5</option>
<option value="6">选项6</option>
<option value="7">选项7</option>
</select>
<div>
<span id="add" >选中添加到右边>></span>
<span id="add_all" >全部添加到右边>></span>
</div>
</div>
<div class="centent">
<select multiple="multiple" id="select2" name="sel" style="width: 100px;height:160px;">
</select>
<div>
<span id="remove"><<选中删除到左边</span>
<span id="remove_all"><<全部删除到左边</span>
</div>
</div>

使用JQuery，Ajax调用动态填充Select的option选项

//绑定ClassLevel1单击事件
$("#ClassLevel1").change(function () {
var id = $("#ClassLevel1").val();
var level2 = $("#ClassLevel2");
level2.empty();
$("#ClassLevel3").hide();
$.ajax({
url: "./askCommon.ashx?action=getclasslevel&pid=" + id,
data: { "type": "ajax" },
datatype: "json",
type: "get",
success: function (data) {
var json = eval_r(data);
for (var ind in json) {
level2.append($("<option value='" + json[ind].id + "'>" + json[ind].typename + "</option>"));
}
}
});
})